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Combining JSP and ServletsThe technology of JSP and Servlet is the most important technology which use Java technology to exploit request of server, and it is also the standard which exploit business application .Java developers prefer to use it for a variety of reasons, one of which is already familiar with the Java language for the development of this technology are easy to learn Java to the other is "a preparation, run everywhere" to bring the concept of Web applications, To achieve a "one-prepared everywhere realized." And more importantly, if followed some of the principles of good design, it can be said of separating and content to create high-quality, reusable, easy to maintain and modify the application. For example, if the document in HTML embedded Java code too much (script), will lead the developed application is extremely complex, difficult to read, it is not easy reuse, but also for future maintenance and modification will also cause difficulties. In fact, CSDN the JSP / Servlet forum, can often see some questions, the code is very long, can logic is not very clear, a large number of HTML and Java code mixed together. This is the random development of the defects.Early dynamic pages mainly CGI (Common Gateway Interface, public Gateway Interface) technology, you can use different languages of the CGI programs, such as VB, C / C + + or Delphi, and so on. Though the technology of CGI is developed and powerful, because of difficulties in programming, and low efficiency, modify complex shortcomings,it is gradually being replaced by the trend. Of all the new technology, JSP / Servlet with more efficient and easy to program, more powerful, more secure and has a good portability, they have been many people believe that the future is the most dynamic site of the future development of technology.Similar to CGI, Servlet support request / response model. When a customer submit a request to the server, the server presented the request Servlet, Servlet responsible for handling requests and generate a response, and then gave the server, and then from the server sent to the customer. And the CGI is different, Servlet not generate a new process, but with HTTP Server at the same process. It threads through the use of technology, reduce the server costs. Servlet handling of the request process is this: When received from the client's request, calling service methods, the method of Servlet arrival of the first judgement is what type of request (GET / POST / HEAD…), then calls the appropriate treatment (DoGet / doP ost / doHead…) and generate a response.Although such a complex, in fact, simply said to Servlet is a Java class. And the general category of the difference is that this type operating in a Servlet container, which can provide session management and targeted life-cycle management. So that when you use the Servlet, you can get all the benefits of the Java platform, including the safety of the management, use JDBC access the database and cross-platform capability. Moreover, Servlet using thread, and can develop more efficient Web applications.JSP technology is a key J2EE technology, it at a higher level of abstraction of a Servlet.It allows conventional static and dynamic HTML content generated by combining an HTML page looks like, but as a Servlet to run. There are many commercial application server support JSP technology, such as BEA WebLogic, IBM WebSphere, JRun, and so on. JSP and Servlet use more than simple. If you have a JSP support for Web servers, and a JSP document, you can put it Fangdao any static HTML files can be placed, do not have to compile, do not have to pack, do not have to ClassPath settings, you can visit as ordinary Web It did visit, the server will automatically help you to do other work.JSP document looks like an ordinary static HTML document, but inside contains a number of Java code. It uses. Jsp the suffix, used to tell the server this document in need of special treatment. When we visit a JSP page, the document will first be translated into a JSP engine Java source files, is actually a Servlet, and compiler, and then, like other Servlet, from Servlet engine to handle. Servlet engine of this type loading, handling requests from customers, and the results returned to the customer, as shown below:Figure 1: Calling the process of JSP pagesAfter another visit this page to the customer, as long as the paper there have been no changes, JSP engine has been loaded directly call the Servlet. If you have already been modified, it will be once again the implementation of the above process, translate, compile and load. In fact, this is the so-called "first person to punishment." Because when the first visit to the implementation of a series of the above process, so will spend some time after such a visit would not.Java servlets offer a powerful API that provides access to all the information about the request, the session, and the application. combining JSP with servlets lets you clearly separate the application logic from the presentation of the application; in other words, it lets you use the most appropriate component type for the roles of Model, View and Controller.Servlets, Filters, and ListenersA servlet is a Java class that extends a server with functionality for processing a request and producing a response. It's implemented using the classes and interfaces defined by the Servlet API. The API consists of two packages: the javax.servlet package contains classes and interfaces that are protocol-independent, while the javax.servlet.http package provides HTTP-specific extensions and utility classes.What makes a servlet a servlet is that the class implements an interface named javax.servlet.Servlet, either directly or by extending one of the support classes. This interface defines the methods used by the web container to manage and interact with theservlet. A servlet for processing HTTP requests typically extends the javax.servlet.http.HttpServlet class. This class implements the Servlet interface and provides additional methods suitable for HTTP processing.Servlet LifecycleThe web container manages all aspects of the servlet's lifecycle. It creates an instance of the servlet class when needed, passes requests to the instance for processing, and eventually removes the instance. For an HttpServlet, the container calls the following methods at the appropriate times in the servlet lifecycle.Besides the doGet( ) and doPost( ) methods, there are methods corresponding to the other HTTP methods: doDelete( ), doHead( ), doOptions( ), doPut( ), and doTrace( ). Typically you don't implement these methods; the HttpServlet class already takes care of HEAD, OPTIONS, and TRACE requests in a way that's suitable for most servlets, and the DELETE and PUT HTTP methods are rarely used in a web application.It's important to realize that the container creates only one instance of each servlet. This means that the servlet must be thread safe -- able to handle multiple requests at the same time, each executing as a separate thread through the servlet code. Without getting lost in details, you satisfy this requirement with regards to instance variables if you modify the referenced objects only in the init( ) and destroy( ) methods, and just read them in the request processing methods.Compiling and Installing a ServletTo compile a servlet, you must first ensure that you have the JAR file containing all Servlet API classes in the CLASSPATH environment variable. The JAR file is distributed with all web containers. Tomcat includes it in a file called servlet.jar, located in the common/lib directory. On a Windows platform, you include the JAR file in the CLASSPATH.. Reading a RequestOne of the arguments passed to the doGet( ) and doPost( ) methods is an object that implements the HttpServletRequest interface. This interface defines methods that provide access to a wealth of information about the request.Generating a ResponseBesides the request object, the container passes an object that implements the HttpServletResponse interface as an argument to the doGet( ) and doPost( ) methods. This interface defines methods for getting a writer or stream for the response body. It also defines methods for setting the response status code and headers.Using Filters and ListenersThe servlet specification defines two component types beside servlets: filters and listeners. These two types were introduced in the Servlet 2.3 specification, so if you're using a container that doesn't yet support this version of the specification, I'm afraid you'reout of luck.FiltersA filter is a component that can intercept a request targeted for a servlet, JSP page, or static page, as well as the response before it's sent to the client. This makes it easy to centralize tasks that apply to all requests, such as access control, logging, and charging for the content or the services offered by the application. A filter has full access to the body and headers of the request and response, so it can also perform various transformations. One example is compressing the response body if the Accept-Language request header indicates that the client can handle a compressed response.A filter can be applied to either a specific servlet or to all requests matching a URL pattern, such as URLs starting with the same path elements or having the same extension. ListenersListeners allow your application to react to certain events. Prior to Servlet 2.3, you could handle only session attribute binding events (triggered when an object was added or removed from a session). You could do this by letting the object saved as a sessionattribute(using the HttpSession.setAttribute() method)implement the HttpSessionBindingListener interface. With the new interfaces introduced in the 2.3 version of the specification, you can create listeners for servlet context and session lifecycle events as well as session activation and passivation events (used by a container that temporarily saves session state to disk or migrates a session to another server). A newsession attribute event listener also makes it possible to deal with attribute binding events for all sessions in one place, instead of placing individual listener objects in each session.The new types of listeners follow the standard Java event model. In other words, a listener is a class that implements one or more of the listener interfaces. The interfaces define methods that correspond to events. The listener class is registered with the container when the application starts, and the container then calls the event methods at the appropriate times.Initializing Shared Resources Using a ListenerBeans like this typically need to be initialized before they can be used. For instance, they may need a reference to a database or some other external data source and may create an initial information cache in memory to provide fast access even to the first request for data. You can include code for initialization of the shared resources in the servlet and JSP pages that need them, but a more modular approach is to place all this code in one place and let the other parts of the application work on the assumption that the resources are already initialized and available. An application lifecycle listener is a perfect tool for this type of resource initialization. This type of listener implements the javax.servlet.ServletContextListener interface, with methods called by the container when the application starts and when it shuts down.Picking the Right Component Type for Each TaskThe Project Billboard application introduced is a fairly complex application. Half thepages are pure controller and business logic processing, it accesses a database to authenticate users, and most pages require access control. In real life, it would likely contain even more pages, for instance, pages for access to a shared document archive, time schedules, and a set of pages for administration. As the application evolves, it may become hard to maintain as a pure JSP application. It's easy to forget to include the access control code in new pages.This is clearly an application that can benefit from using a combination of JSP pages and the component types defined by the servlet specification for the MVC roles. Let's look at the main requirements and see how we can map them to appropriate component types:●Database access should be abstracted, to avoid knowledge of a specific dataschema or database engine in more than one part of the application: beans in therole of Model can be used to accomplish this.●The database access beans must be made available to all other parts of theapplication when it starts: an application lifecycle event listener is the perfectcomponent type for this task.●Only authenticated users must be allowed to use the application: a filter canperform access control to satisfy this requirement.●Request processing is best done with Java code: a servlet, acting as the Controller,fits the bill.●It must be easy to change the presentation: this is where JSP shines, acting as theView.Adding servlets, listeners, and filters to the mix minimizes the need for complex logic in the JSP pages. Placing all this code in Java classes instead makes it possible to use a regular Java compiler and debugger to fix potential problems.Centralized Request Processing Using a ServletWith a servlet as the common entry point for all application requests, you gain control over the page flow of the application. The servlet can decide which type of response to generate depending on the outcome of the requested action, such as returning a common error page for all requests that fail, or different responses depending on the type of client making the request. With the help from some utility classes, it can also provide services such as input validation, I18N preparations, and in general, encourage a more streamlined approach to request handling.When you use a servlet as a Controller, you must deal with the following basic requirements:●All requests for processing must be passed to the single Controller servlet.●The servlet must be able to distinguish requests for different types of processing.Here are other features you will want support for, even though they may not be requirements for all applications:● A strategy for extending the application to support new types of processingA mechanism for changing the page flow of the application without modifyingcode.Mapping Application Requests to the ServletThe first requirement for using a Controller servlet is that all requests must pass through it. This can be satisfied in many ways. If you have played around a bit with servlets previously, you're probably used to invoking a servlet with a URI that starts with /myApp/servlet. This is a convention introduced by Suns Java Web Server (JWS), the first product to support servlets before the API was standardized. Most servlet containers support this convention today, even though it's not formally defined in the servlet specification.将Servlet和JSP组合使用Servlet和JSP技术是用Java开发服务器端应用的主要技术，是开发商务应用表示端的标准。
Overview of JSP TechnologyBy: Kathy Sierra and Bert BatesSource:Servlet & JSPThe Java Server Pages( JSP) is a kind of according to web of the script plait distance technique, similar carries the script language of Java in the server of the Netscape company of server- side JavaScript( SSJS) and the Active Server Pages(ASP) of the Microsoft. JSP compares the SSJS and ASP to have better can expand sex, and it is no more exclusive than any factory or some one particular server of Web. Though the norm of JSP is to be draw up by Sun company of, any factory can carry out the JSP on own system.The After Sun release the JSP (the Java Server Pages) formally, the this kind of new Web application development technique very quickly caused the people's concern. JSP provided a special development environment for the Web application that establishes the high dynamic state. According to the Sun parlance, the JSP can adapt to include the Apache WebServer, IIS4.0 on the market at inside of 85% server product.This chapter will introduce the related knowledge of JSP and Databases, and JavaBean related contents, is all certainly rougher introduction among them basic contents, say perhaps to is a Guide only, if the reader needs the more detailed information, pleasing the book of consult the homologous JSP.1.1 GENERALIZEThe JSP (Java Server Pages) is from the company of Sun Microsystems initiate, the many companies the participate to the build up the together of the a kind the of dynamic the state web the page technique standard, the it have the it in the construction the of the dynamic state the web page the strong but the do not the especially of the function. JSP and the technique of ASP of the Microsoft are very alike. Both all provide the ability that mixes with a certain procedure code and is explain by the language engine to carry out the procedure code in the code of HTML. Underneath we are simple of carry on the introduction to it.JSP pages are translated into servlets. So, fundamentally, any task JSP pages can perform could also be accomplished by servlets. However, this underlying equivalence does not mean that servlets and JSP pages are equally appropriate in allscenarios. The issue is not the power of the technology, it is the convenience, productivity, and maintainability of one or the other. After all, anything you can do on a particular computer platform in the Java programming language you could also do in assembly language. But it still matters which you choose.JSP provides the following benefits over servlets alone:• It is easier to write and maintain the HTML. Your static code is ordinary HTML: no extra backslashes, no double quotes, and no lurking Java syntax.• You can use standard Web-site development tools. Even HTML tools that know nothing about JSP can be used because they simply ignore the JSP tags.• You can divide up your development team. The Java programmers can work on the dynamic code. The Web developers can concentrate on the presentation layer. On large projects, this division is very important. Depending on the size of your team and the complexity of your project, you can enforce a weaker or stronger separation between the static HTML and the dynamic content.Now, this discussion is not to say that you should stop using servlets and use only JSP instead. By no means. Almost all projects will use both. For some requests in your project, you will use servlets. For others, you will use JSP. For still others, you will combine them with the MVC architecture. You want the appropriate tool for the job, and servlets, by themselves, do not complete your toolkit.1.2 SOURCE OF JSPThe technique of JSP of the company of Sun, making the page of Web develop the personnel can use the HTML perhaps marking of XML to design to turn the end page with format. Use the perhaps small script future life of marking of JSP becomes the dynamic state on the page contents. (the contents changes according to the claim of)The Java Servlet is a technical foundation of JSP, and the large Web applies the development of the procedure to need the Java Servlet to match with the JSP and then can complete, this name of Servlet comes from the Applet, the local translation method of now is a lot of, this book in order not to misconstruction, decide the direct adoption Servlet but don't do any translation, if reader would like to, can call it as" small service procedure". The Servlet is similar to traditional CGI, ISAPI, NSAPI etc. Web procedure development the function of the tool in fact, at use the Java Servlet hereafter, the customer need not use again the lowly method of CGI of efficiency, also need not use only the ability come to born page of Web of dynamic state in themethod of API that a certain fixed Web server terrace circulate. Many servers of Web all support the Servlet, even not support the Servlet server of Web directly and can also pass the additional applied server and the mold pieces to support the Servlet. Receive benefit in the characteristic of the Java cross-platform, the Servlet is also a terrace irrelevant, actually, as long as match the norm of Java Servlet, the Servlet is complete to have nothing to do with terrace and is to have nothing to do with server of Web. Because the Java Servlet is internal to provide the service by the line distance, need not start a progress to the each claims, and make use of the multi-threading mechanism can at the same time for several claim service, therefore the efficiency of Java Servlet is very high.But the Java Servlet also is not to has no weakness, similar to traditional CGI, ISAPI, the NSAPI method, the Java Servlet is to make use of output the HTML language sentence to carry out the dynamic state web page of, if develop the whole website with the Java Servlet, the integration process of the dynamic state part and the static state page is an evil-foreboding dream simply. For solving this kind of weakness of the Java Servlet, the SUN released the JSP.A number of years ago, Marty was invited to attend a small 20-person industry roundtable discussion on software technology. Sitting in the seat next to Marty was James Gosling, inventor of the Java programming language. Sitting several seats away was a high-level manager from a very large software company in Redmond, Washington. During the discussion, the moderator brought up the subject of Jini, which at that time was a new Java technology. The moderator asked the manager what he thought of it, and the manager responded that it was too early to tell, but that it seemed to be an excellent idea. He went on to say that they would keep an eye on it, and if it seemed to be catching on, they would follow his company's usual "embrace and extend" strategy. At this point, Gosling lightheartedly interjected "You mean disgrace and distend."Now, the grievance that Gosling was airing was that he felt that this company would take technology from other companies and suborn it for their own purposes. But guess what? The shoe is on the other foot here .The Java community did not invent the idea of designing pages as a mixture of static HTML and dynamic code marked with special tags. For example, Cold Fusion did it years earlier. Even ASP (a product from the very software company of the aforementioned manager) popularized this approach before JSP came along and decided to jump on the bandwagon. In fact,JSP not only adopted the general idea, it even used many of the same special tags as ASP did.The JSP is an establishment at the model of Java servlets on of the expression layer technique, it makes plait write the HTML to become more simple. Be like the SSJS, it also allows you carry the static state HTML contents and servers the script mix to put together the born dynamic state exportation. JSP the script language that the Java is the tacit approval, however, be like the ASP and can use other languages( such as JavaScript and VBScript), the norm of JSP also allows to use other languages.1.3JSP CHARACTERISTICSIs a service according to the script language in some one language of the statures system this kind of discuss, the JSP should be see make is a kind of script language. However, be a kind of script language, the JSP seemed to be too strong again, almost can use all Javas in the JSP.Be a kind of according to text originally of, take manifestation as the central development technique, the JSP provided all advantages of the Java Servlet, and, when combine with a JavaBeans together, providing a kind of make contents and manifestation that simple way that logic separate. Separate the contents and advantage of logical manifestations is, the personnel who renews the page external appearance need not know the code of Java, and renew the JavaBeans personnel also need not be design the web page of expert in hand, can use to take the page of JavaBeans JSP to define the template of Web, to build up a form have the alike external appearance of the website that page constitute. JavaBeans completes the data to provide, having no code of Java in the template thus, this means that these templates can be written the personnel by a HTML plait to support. Certainly, can also make use of the Java Servlet to control the logic of the website, adjust through the Java Servlet to use the way of the document of JSP to separate website of logic and contents.Generally speaking, in actual engine of JSP, the page of JSP is the edit and translate type while carry out, not explain the type of. Explain the dynamic state web page development tool of the type, such as ASP, PHP3 etc., because speed etc. reason, have already can't satisfy current the large electronic commerce needs applied, traditional development techniques are all at to edit and translate the executive way change, such as the ASP → ASP+;PHP3 → PHP4.In the JSP norm book, did not request the procedure in the JSP code part (becalled the Scriptlet) and must write with the Java definitely. Actually, have some engines of JSP are adoptive other script languages such as the EMAC- Script, etc., but actually this a few script languages also are to set up on the Java, edit and translate for the Servlet to carry out of. Write according to the norm of JSP, have no Scriptlet of relation with Java also is can of, however, mainly lie in the ability and JavaBeans, the Enterprise JavaBeans because of the JSP strong function to work together, so even is the Scriptlet part not to use the Java, edit and translate of performance code also should is related with Java.1.4Advantages of JSP Over Competing TechnologiesA number of years ago, Marty was invited to attend a small 20-person industry roundtable discussion on software technology. Sitting in the seat next to Marty was James Gosling, inventor of the Java programming language. Sitting several seats away was a high-level manager from a very large software company in Redmond, Washington. During the discussion, the moderator brought up the subject of Jini, which at that time was a new Java technology. The moderator asked the manager what he thought of it, and the manager responded that it was too early to tell, but that it seemed to be an excellent idea. He went on to say that they would keep an eye on it, and if it seemed to be catching on, they would follow his company's usual "embrace and extend" strategy. At this point, Gosling lightheartedly interjected "You mean disgrace and distend."Now, the grievance that Gosling was airing was that he felt that this company would take technology from other companies and suborn it for their own purposes. But guess what? The shoe is on the other foot here. The Java community did not invent the idea of designing pages as a mixture of static HTML and dynamic code marked with special tags. For example, ColdFusion did it years earlier. Even ASP (a product from the very software company of the aforementioned manager) popularized this approach before JSP came along and decided to jump on the bandwagon. In fact, JSP not only adopted the general idea, it even used many of the same special tags as ASP did.So, the question becomes: why use JSP instead of one of these other technologies? Our first response is that we are not arguing that everyone should. Several of those other technologies are quite good and are reasonable options in some situations. In other situations, however, JSP is clearly better. Here are a few of the reasons.Versus .NET and Active Server Pages (ASP).NET is well-designed technology from Microsoft. is the part that directly competes with servlets and JSP. The advantages of JSP are twofold.First, JSP is portable to multiple operating systems and Web servers; you aren't locked into deploying on Windows and IIS. Although the core .NET platform runs on a few non-Windows platforms, the ASP part does not. You cannot expect to deploy serious applications on multiple servers and operating systems. For some applications, this difference does not matter. For others, it matters greatly.Second, for some applications the choice of the underlying language matters greatly. For example, although .NET's C# language is very well designed and is similar to Java, fewer programmers are familiar with either the core C# syntax or the many auxiliary libraries. In addition, many developers still use the original version of ASP. With this version, JSP has a clear advantage for the dynamic code. With JSP, the dynamic part is written in Java, not VBScript or another ASP-specific language, so JSP is more powerful and better suited to complex applications that require reusable components.You could make the same argument when comparing JSP to the previous version of ColdFusion; with JSP you can use Java for the "real code" and are not tied to a particular server product. However, the current release of ColdFusion is within the context of a J2EE server, allowing developers to easily mix ColdFusion and servlet/JSP code.Versus PHPPHP (a recursive acronym for "PHP: Hypertext Preprocessor") is a free, open-source, HTML-embedded scripting language that is somewhat similar to both ASP and JSP. One advantage of JSP is that the dynamic part is written in Java, which already has an extensive API for networking, database access, distributed objects, and the like, whereas PHP requires learning an entirely new, less widely used language. A second advantage is that JSP is much more widely supported by tool and server vendors than is PHP.Versus Pure ServletsJSP doesn't provide any capabilities that couldn't, in principle, be accomplished with servlets. In fact, JSP documents are automatically translated into servlets behind the scenes. But it is more convenient to write (and to modify!) regular HTML than to use a zillion println statements to generate the HTML. Plus, by separating the presentation from the content, you can put different people on different tasks: yourWeb page design experts can build the HTML by using familiar tools and either leave places for your servlet programmers to insert the dynamic content or invoke the dynamic content indirectly by means of XML tags.Does this mean that you can just learn JSP and forget about servlets? Absolutely not! JSP developers need to know servlets for four reasons:1. JSP pages get translated into servlets. You can't understand how JSP works without understanding servlets.2. JSP consists of static HTML, special-purpose JSP tags, and Java code. What kind of Java code? Servlet code! You can't write that code if you don't understand servlet programming.3. Some tasks are better accomplished by servlets than by JSP. JSP is good at generating pages that consist of large sections of fairly well structured HTML or other character data. Servlets are better for generating binary data, building pages with highly variable structure, and performing tasks (such as redirection) that involve little or no output.4. Some tasks are better accomplished by a combination of servlets and JSP than by either servlets or JSP alone.Versus JavaScriptJavaScript, which is completely distinct from the Java programming language, is normally used to dynamically generate HTML on the client, building parts of the Web page as the browser loads the document. This is a useful capability and does not normally overlap with the capabilities of JSP (which runs only on the server). JSP pages still include SCRIPT tags for JavaScript, just as normal HTML pages do. In fact, JSP can even be used to dynamically generate the JavaScript that will be sent to the client. So, JavaScript is not a competing technology; it is a complementary one.It is also possible to use JavaScript on the server, most notably on Sun ONE (formerly iPlanet), IIS, and BroadVision servers. However, Java is more powerful, flexible, reliable, and portable.1.5JSP MECHANISMTo comprehend the JSP how unite the technical advantage that above various speak of, come to carry out various result easily, the customer must understand the differentiation of" the module develops for the web page of the center" and" the page develops for the web page of the center" first.The SSJS and ASP are all in several year ago to release, the network of that time is still very young, no one knows to still have in addition to making all business, datas and the expression logic enter the original web page entirely heap what better solve the method. This kind of model that take page as the center studies and gets the very fast development easily. However, along with change of time, the people know that this kind of method is unwell in set up large, the Web that can upgrade applies the procedure. The expression logic write in the script environment was lock in the page, only passing to shear to slice and glue to stick then can drive heavy use. Express the logic to usually mix together with business and the data logics, when this makes be the procedure member to try to change an external appearance that applies the procedure but do not want to break with its llied business logic, apply the procedure of maintenance be like to walk the similar difficulty on the eggshell. In fact in the business enterprise, heavy use the application of the module already through very mature, no one would like to rewrite those logics for their applied procedure.HTML and sketch the designer handed over to the implement work of their design the Web plait the one who write, make they have to double work- Usually is the handicraft plait to write, because have no fit tool and can carry the script and the HTML contents knot to the server to put together. Chien but speech, apply the complexity of the procedure along with the Web to promote continuously, the development method that take page as the center limits sex to become to get up obviously.At the same time, the people always at look for the better method of build up the Web application procedure, the module spreads in customer's machine/ server the realm. JavaBeans and ActiveX were published the company to expand to apply the procedure developer for Java and Windows to use to come to develop the complicated procedure quickly by" the fast application procedure development"( RAD) tool. These techniques make the expert in the some realm be able to write the module for the perpendicular application plait in the skill area, but the developer can go fetch the usage directly but need not control the expertise of this realm.Be a kind of take module as the central development terrace, the JSP appeared. It with the JavaBeans and Enterprise JavaBeans( EJB) module includes the model of the business and the data logic for foundation, provide a great deal of label and a script terraces to use to come to show in the HTML page from the contents of JavaBeans creation or send a present in return. Because of the property that regards the moduleas the center of the JSP, it can drive Java and not the developer of Java uses equally. Not the developer of Java can pass the JSP label( Tags) to use the JavaBeans that the deluxe developer of Java establish. The developer of Java not only can establish and use the JavaBeans, but also can use the language of Java to come to control more accurately in the JSP page according to the expression logic of the first floor JavaBeans.See now how JSP is handle claim of HTTP. In basic claim model, a claim directly was send to JSP page in. The code of JSP controls to carry on hour of the logic processing and module of JavaBeans' hand over with each other, and the manifestation result in dynamic state bornly, mixing with the HTML page of the static state HTML code. The Beans can be JavaBeans or module of EJBs. Moreover, the more complicated claim model can see make from is request other JSP pages of the page call sign or Java Servlets.The engine of JSP wants to chase the code of Java that label of JSP, code of Java in the JSP page even all converts into the big piece together with the static state HTML contents actually. These codes piece was organized the Java Servlet that customer cannot see to go to by the engine of JSP, then the Servlet edits and translate them automatically byte code of Java.Thus, the visitant that is the website requests a JSP page, under the condition of it is not knowing, an already born, the Servlet actual full general that prepared to edit and translate completes all works, very concealment but again and efficiently. The Servlet is to edit and translate of, so the code of JSP in the web page does not need when the every time requests that page is explain. The engine of JSP need to be edit and translate after Servlet the code end is modify only once, then this Servlet that edited and translate can be carry out. The in view of the fact JSP engine auto is born to edit and translate the Servlet also, need not procedure member begins to edit and translate the code, so the JSP can bring vivid sex that function and fast developments need that you are efficiently.Compared with the traditional CGI, the JSP has the equal advantage. First, on the speed, the traditional procedure of CGI needs to use the standard importation of the system to output the equipments to carry out the dynamic state web page born, but the JSP is direct is mutually the connection with server. And say for the CGI, each interview needs to add to add a progress to handle, the progress build up and destroy by burning constantly and will be a not small burden for calculator of be the server ofWeb. The next in order, the JSP is specialized to develop but design for the Web of, its purpose is for building up according to the Web applied procedure, included the norm and the tool of the whole set. Use the technique of JSP can combine a lot of JSP pages to become a Web application procedure very expediently.。
Combining JSP and ServletsThe technology of JSP and Servlet is the most important technology which use Java technology to exploit request of server, and it is also the standard which exploit business application .Java developers prefer to use it for a variety of reasons, one of which is already familiar with the Java language for the development of this technology are easy to learn Java to the other is "a preparation, run everywhere" to bring the concept of Web applications, To achieve a "one-prepared everywhere realized." And more importantly, if followed some of the principles of good design, it can be said of separating and content to create high-quality, reusable, easy to maintain and modify the application. For example, if the document in HTML embedded Java code too much (script), will lead the developed application is extremely complex, difficult to read, it is not easy reuse, but also for future maintenance and modification will also cause difficulties. In fact, CSDN the JSP / Servlet forum, can often see some questions, the code is very long, can logic is not very clear, a large number of HTML and Java code mixed together. This is the random development of the defects.Early dynamic pages mainly CGI (Common Gateway Interface, public Gateway Interface) technology, you can use different languages of the CGI programs, such as VB, C / C + + or Delphi, and so on. Though the technology of CGI is developed and powerful, because of difficulties in programming, and low efficiency, modify complex shortcomings,it is gradually being replaced by the trend. Of all the new technology, JSP / Servlet with more efficient and easy to program, more powerful, more secure and has a good portability, they have been many people believe that the future is the most dynamic site of the future development of technology.Similar to CGI, Servlet support request / response model. When a customer submit a request to the server, the server presented the request Servlet, Servlet responsible for handling requests and generate a response, and then gave the server, and then from the server sent to the customer. And the CGI is different, Servlet not generate a new process, but with HTTP Server at the same process. It threads through the use of technology, reduce the server costs. Servlet handling of the request process is this: When received from the client's request, calling service methods, the method of Servlet arrival of the first judgement is what type of request (GET / POST / HEAD…), then calls the appropriate treatment (DoGet / doP ost / doHead…) and generate a response.Although such a complex, in fact, simply said to Servlet is a Java class. And the general category of the difference is that this type operating in a Servlet container, which can provide session management and targeted life-cycle management. So that when you use the Servlet, you can get all the benefits of the Java platform, including the safety of the management, use JDBC access the database and cross-platform capability. Moreover, Servlet using thread, and can develop more efficient Web applications.JSP technology is a key J2EE technology, it at a higher level of abstraction of a Servlet.It allows conventional static and dynamic HTML content generated by combining an HTML page looks like, but as a Servlet to run. There are many commercial application server support JSP technology, such as BEA WebLogic, IBM WebSphere, JRun, and so on. JSP and Servlet use more than simple. If you have a JSP support for Web servers, and a JSP document, you can put it Fangdao any static HTML files can be placed, do not have to compile, do not have to pack, do not have to ClassPath settings, you can visit as ordinary Web It did visit, the server will automatically help you to do other work.JSP document looks like an ordinary static HTML document, but inside contains a number of Java code. It uses. Jsp the suffix, used to tell the server this document in need of special treatment. When we visit a JSP page, the document will first be translated into a JSP engine Java source files, is actually a Servlet, and compiler, and then, like other Servlet, from Servlet engine to handle. Servlet engine of this type loading, handling requests from customers, and the results returned to the customer, as shown below:Figure 1: Calling the process of JSP pagesAfter another visit this page to the customer, as long as the paper there have been no changes, JSP engine has been loaded directly call the Servlet. If you have already been modified, it will be once again the implementation of the above process, translate, compile and load. In fact, this is the so-called "first person to punishment." Because when the first visit to the implementation of a series of the above process, so will spend some time after such a visit would not.Java servlets offer a powerful API that provides access to all the information about the request, the session, and the application. combining JSP with servlets lets you clearly separate the application logic from the presentation of the application; in other words, it lets you use the most appropriate component type for the roles of Model, View and Controller.Servlets, Filters, and ListenersA servlet is a Java class that extends a server with functionality for processing a request and producing a response. It's implemented using the classes and interfaces defined by the Servlet API. The API consists of two packages: the javax.servlet package contains classes and interfaces that are protocol-independent, while the javax.servlet.http package provides HTTP-specific extensions and utility classes.What makes a servlet a servlet is that the class implements an interface named javax.servlet.Servlet, either directly or by extending one of the support classes. This interface defines the methods used by the web container to manage and interact with theservlet. A servlet for processing HTTP requests typically extends the javax.servlet.http.HttpServlet class. This class implements the Servlet interface and provides additional methods suitable for HTTP processing.Servlet LifecycleThe web container manages all aspects of the servlet's lifecycle. It creates an instance of the servlet class when needed, passes requests to the instance for processing, and eventually removes the instance. For an HttpServlet, the container calls the following methods at the appropriate times in the servlet lifecycle.Besides the doGet( ) and doPost( ) methods, there are methods corresponding to the other HTTP methods: doDelete( ), doHead( ), doOptions( ), doPut( ), and doTrace( ). Typically you don't implement these methods; the HttpServlet class already takes care of HEAD, OPTIONS, and TRACE requests in a way that's suitable for most servlets, and the DELETE and PUT HTTP methods are rarely used in a web application.It's important to realize that the container creates only one instance of each servlet. This means that the servlet must be thread safe -- able to handle multiple requests at the same time, each executing as a separate thread through the servlet code. Without getting lost in details, you satisfy this requirement with regards to instance variables if you modify the referenced objects only in the init( ) and destroy( ) methods, and just read them in the request processing methods.Compiling and Installing a ServletTo compile a servlet, you must first ensure that you have the JAR file containing all Servlet API classes in the CLASSPATH environment variable. The JAR file is distributed with all web containers. Tomcat includes it in a file called servlet.jar, located in the common/lib directory. On a Windows platform, you include the JAR file in the CLASSPATH.. Reading a RequestOne of the arguments passed to the doGet( ) and doPost( ) methods is an object that implements the HttpServletRequest interface. This interface defines methods that provide access to a wealth of information about the request.Generating a ResponseBesides the request object, the container passes an object that implements the HttpServletResponse interface as an argument to the doGet( ) and doPost( ) methods. This interface defines methods for getting a writer or stream for the response body. It also defines methods for setting the response status code and headers.Using Filters and ListenersThe servlet specification defines two component types beside servlets: filters and listeners. These two types were introduced in the Servlet 2.3 specification, so if you're using a container that doesn't yet support this version of the specification, I'm afraid you'reout of luck.FiltersA filter is a component that can intercept a request targeted for a servlet, JSP page, or static page, as well as the response before it's sent to the client. This makes it easy to centralize tasks that apply to all requests, such as access control, logging, and charging for the content or the services offered by the application. A filter has full access to the body and headers of the request and response, so it can also perform various transformations. One example is compressing the response body if the Accept-Language request header indicates that the client can handle a compressed response.A filter can be applied to either a specific servlet or to all requests matching a URL pattern, such as URLs starting with the same path elements or having the same extension. ListenersListeners allow your application to react to certain events. Prior to Servlet 2.3, you could handle only session attribute binding events (triggered when an object was added or removed from a session). You could do this by letting the object saved as a sessionattribute(using the HttpSession.setAttribute() method)implement the HttpSessionBindingListener interface. With the new interfaces introduced in the 2.3 version of the specification, you can create listeners for servlet context and session lifecycle events as well as session activation and passivation events (used by a container that temporarily saves session state to disk or migrates a session to another server). A newsession attribute event listener also makes it possible to deal with attribute binding events for all sessions in one place, instead of placing individual listener objects in each session.The new types of listeners follow the standard Java event model. In other words, a listener is a class that implements one or more of the listener interfaces. The interfaces define methods that correspond to events. The listener class is registered with the container when the application starts, and the container then calls the event methods at the appropriate times.Initializing Shared Resources Using a ListenerBeans like this typically need to be initialized before they can be used. For instance, they may need a reference to a database or some other external data source and may create an initial information cache in memory to provide fast access even to the first request for data. You can include code for initialization of the shared resources in the servlet and JSP pages that need them, but a more modular approach is to place all this code in one place and let the other parts of the application work on the assumption that the resources are already initialized and available. An application lifecycle listener is a perfect tool for this type of resource initialization. This type of listener implements the javax.servlet.ServletContextListener interface, with methods called by the container when the application starts and when it shuts down.Picking the Right Component Type for Each TaskThe Project Billboard application introduced is a fairly complex application. Half thepages are pure controller and business logic processing, it accesses a database to authenticate users, and most pages require access control. In real life, it would likely contain even more pages, for instance, pages for access to a shared document archive, time schedules, and a set of pages for administration. As the application evolves, it may become hard to maintain as a pure JSP application. It's easy to forget to include the access control code in new pages.This is clearly an application that can benefit from using a combination of JSP pages and the component types defined by the servlet specification for the MVC roles. Let's look at the main requirements and see how we can map them to appropriate component types:●Database access should be abstracted, to avoid knowledge of a specific dataschema or database engine in more than one part of the application: beans in therole of Model can be used to accomplish this.●The database access beans must be made available to all other parts of theapplication when it starts: an application lifecycle event listener is the perfectcomponent type for this task.●Only authenticated users must be allowed to use the application: a filter canperform access control to satisfy this requirement.●Request processing is best done with Java code: a servlet, acting as the Controller,fits the bill.●It must be easy to change the presentation: this is where JSP shines, acting as theView.Adding servlets, listeners, and filters to the mix minimizes the need for complex logic in the JSP pages. Placing all this code in Java classes instead makes it possible to use a regular Java compiler and debugger to fix potential problems.Centralized Request Processing Using a ServletWith a servlet as the common entry point for all application requests, you gain control over the page flow of the application. The servlet can decide which type of response to generate depending on the outcome of the requested action, such as returning a common error page for all requests that fail, or different responses depending on the type of client making the request. With the help from some utility classes, it can also provide services such as input validation, I18N preparations, and in general, encourage a more streamlined approach to request handling.When you use a servlet as a Controller, you must deal with the following basic requirements:●All requests for processing must be passed to the single Controller servlet.●The servlet must be able to distinguish requests for different types of processing.Here are other features you will want support for, even though they may not be requirements for all applications:● A strategy for extending the application to support new types of processingA mechanism for changing the page flow of the application without modifyingcode.Mapping Application Requests to the ServletThe first requirement for using a Controller servlet is that all requests must pass through it. This can be satisfied in many ways. If you have played around a bit with servlets previously, you're probably used to invoking a servlet with a URI that starts with /myApp/servlet. This is a convention introduced by Suns Java Web Server (JWS), the first product to support servlets before the API was standardized. Most servlet containers support this convention today, even though it's not formally defined in the servlet specification.将Servlet和JSP组合使用Servlet和JSP技术是用Java开发服务器端应用的主要技术，是开发商务应用表示端的标准。
外文原文Overview of JSP Technology and JSP application frameworksAutor: Zambon Giulio/ Sekler MichaelSource: Springer-Verlag New York Inc1．Benefits of JSPJSP pages are translated into servlets. So, fundamentally, any task JSP pages can perform could also be accomplished by servlets. However, this underlying equivalence does not mean that servlets and JSP pages are equally appropriate in all scenarios. The issue is not the power of the technology, it is the convenience, productivity, and maintainability of one or the other. After all, anything you can do on a particular computer platform in the Java programming language you could also do in assembly language. But it still matters which you choose.JSP provides the following benefits over servlets alone: •It is easier to write and maintain the HTML. Your static code is ordinary HTML: no extra backslashes, no double quotes, and no lurking Java syntax.• You can use standard Web-site development tools. Even HTML tools that know nothing about JSP can be used because they simply ignore the JSP tags.• You can divide up your development team. The Java programmers can work on the dynamic code. The Web developers can concentrate on the presentation layer. On large projects, this division is very important. Depending on the size of your team and the complexity of your project, you can enforce a weaker or stronger separation between the static HTML and the dynamic content.Now, this discussion is not to say that you should stop using servlets and use only JSP instead. By no means. Almost all projects will use both. For some requests in your project, you will use servlets. For others, you will use JSP. For still others, you will combine them with the MVC architecture . You want the appropriate tool for the job, and servlets, by themselves, do not complete your toolkit.2.Advantages of JSP Over Competing TechnologiesA number of years ago, Marty was invited to attend a small 20-person industry roundtable discussion on software technology. Sitting in the seat next to Marty was James Gosling, inventor of the Java programming language. Sitting several seats away was a high-level manager from a very large software company in Redmond, Washington. During the discussion, the moderator brought up the subject of Jini,which at that time was a new Java technology. The moderator asked the manager what he thought of it, and the manager responded that it was too early to tell, but that it seemed to be an excellent idea. He went on to say that they would keep an eye on it, and if it seemed to be catching on, they would follow his company's usual "embrace and extend" strategy. At this point, Gosling lightheartedly interjected "You mean disgrace and distend."Now, the grievance that Gosling was airing was that he felt that this company would take technology from other companies and suborn it for their own purposes. But guess what? The shoe is on the other foot here. The Java community did not invent the idea of designing pages as a mixture of static HTML and dynamic code marked with special tags. For example, ColdFusion did it years earlier. Even ASP (a product from the very software company of the aforementioned manager) popularized this approach before JSP came along and decided to jump on the bandwagon. In fact, JSP not only adopted the general idea, it even used many of the same special tags as ASP did..So, the question becomes: why use JSP instead of one of these other technologies? Our first response is that we are not arguing that everyone should. Several of those other technologies are quite good and are reasonable options in some situations. In other situations, however, JSP is clearly better. Here are a few of the reasons.2.1 Versus .NET and Active Server Pages (ASP). NET is well-designed technology from Microsoft. is the part that directly competes with servlets and JSP. The advantages of JSP are two fold.First, JSP is portable to multiple operating systems and Web servers; you aren't locked into deploying on Windows and IIS. Although the core .NET platform runs on a few non-Windows platforms, the ASP part does not. You cannot expect to deploy serious applications on multiple servers and operating systems. For some applications, this difference does not matter. For others, it matters greatly.Second, for some applications the choice of the underlying language matters greatly. For example, although .NET's C# language is very well designed and is similar to Java, fewer programmers are familiar with either the core C# syntax or the many auxiliary libraries. In addition, many developers still use the original version of ASP. With this version, JSP has a clear advantage for the dynamic code. With JSP, the dynamic part is written in Java, not VBScript or another ASP-specific language, so JSP is more powerful and better suited to complex applications that require reusable components.You could make the same argument when comparing JSP to the previous version of ColdFusion; with JSP you can use Java for the "real code" and are not tied to a particular server product. However, the current release of ColdFusion is within the context of a J2EE server, allowing developers to easily mix ColdFusion and servlet/JSP code.2.2 Versus PHPPHP (a recursive acronym for "PHP: Hypertext Preprocessor") is a free, open-source, HTML-embedded scripting language that is somewhat similar to both ASP and JSP. One advantage of JSP is that the dynamic part is written in Java, which already has an extensive API for networking, database access, distributed objects, and the like, whereas PHP requires learning an entirely new, less widely used language. A second advantage is that JSP is much more widely supported by tool and server vendors than is PHP.2.3 Versus Pure ServletsJSP doesn't provide any capabilities that couldn't, in principle, be accomplished with servlets. In fact, JSP documents are automatically translated into servlets behind the scenes. But it is more convenient to write (and to modify!) regular HTML than to use a zillion println statements to generate the HTML. Plus, by separating the presentation from the content, you can put different people on different tasks: your Web page design experts can build the HTML by using familiar tools and either leave places for your servlet programmers to insert the dynamic content or invoke the dynamic content indirectly by means of XML tags.Does this mean that you can just learn JSP and forget about servlets? Absolutely not! JSP developers need to know servlets for four reasons:1. JSP pages get translated into servlets. You can't understand how JSP works without understanding servlets.2. JSP consists of static HTML, special-purpose JSP tags, and Java code. What kind of Java code? Servlet code! You can't write that code if you don't understand servlet programming.3. Some tasks are better accomplished by servlets than by JSP. JSP is good at generating pages that consist of large sections of fairly well structured HTML or other character data. Servlets are better for generating binary data,building pages with highly variable structure, and performing tasks (such as redirection) that involve little or no output.4. Some tasks are better accomplished by a combination of servlets and JSP than by either servlets or JSP alone.2.4 Versus JavaScriptJavaScript, which is completely distinct from the Java programming language, is normally used to dynamically generate HTML on the client, building parts of the Web page as the browser loads the document. This is a useful capability and does not normally overlap with the capabilities of JSP (which runs only on the server). JSP pages still include SCRIPT tags for JavaScript, just as normal HTML pages do. In fact, JSP can even be used to dynamically generate the JavaScript that will be sent to the client. So, JavaScript is not a competing technology; it is a complementary one.It is also possible to use JavaScript on the server, most notably on Sun ONE (formerly iPlanet), IIS, and BroadVision servers. However, Java is more powerful, flexible, reliable, and portable.2.5 Versus WebMacro or VelocityJSP is by no means perfect. Many people have pointed out features that could be improved. This is a good thing, and one of the advantages of JSP is that the specification is controlled by a community that draws from many different companies. So, the technology can incorporate improvements in successive releases.However, some groups have developed alternative Java-based technologies to try to address these deficiencies. This, in our judgment, is a mistake. Using a third-party tool like Apache Struts that augments JSP and servlet technology is a good idea when that tool adds sufficient benefit to compensate for the additional complexity. But using a nonstandard tool that tries to replace JSP is a bad idea. When choosing a technology, you need to weigh many factors: standardization, portability, integration, industry support, and technical features. The arguments for JSP alternatives have focused almost exclusively on the technical features part. But portability, standardization, and integration are also very important. For example, the servlet and JSP specifications define a standard directory structure for Web applications and provide standard files (.war files) for deploying Web applications. All JSP-compatible servers must support these standards. Filters can be set up toapply to any number of servlets or JSP pages, but not to nonstandard resources. The same goes for Web application security settings.Besides, the tremendous industry support for JSP and servlet technology results in improvements that mitigate many of the criticisms of JSP. For example, the JSP Standard Tag Library and the JSP 2.0 expression language address two of the most well-founded criticisms: the lack of good iteration constructs and the difficulty of accessing dynamic results without using either explicit Java code or verbose jsp:useBean elements.3. Misconceptions About JSPForgetting JSP Is Server-Side TechnologyHere are some typical questions Marty has received (most of them repeatedly). • Our server is running JDK 1.4. So, how do I put a Swing component in a JSP page?•How do I put an image into a JSP page? I do not know the proper Java I/O commands to read image files.• Since Tomcat does not support JavaScript, how do I make images that are highlighted when the user moves the mouse over them?• Our clients use older browsers that do not understand JSP. What should we do?• When our clients use "View Source" in a browser, how can I prevent them from seeing the JSP tags?All of these questions are based upon the assumption that browsers know something about the server-side process. But they do not. Thus:• For putting applets with Swing components into Web pages, what matters is the browser's Java version—the server's version is irrelevant. If the browser supports the Java 2 platform, you use the normal APPLET (or Java plug-in) tag and would do so even if you were using non-Java technology on the server. • You do not need Java I/O to read image files; you just put the image in the directory for Web resources (i.e., two levels up from WEB-INF/classes) and output a normal IMG tag.•You create images that change under the mouse by using client-side JavaScript, referenced with the SCRIPT tag; this does not change just because the server is using JSP.• Browsers do not "support" JSP at all—they merely see the output of the JSP page. So, make sure your JSP outputs HTML compatible with the browser, just asyou would do with static HTML pages.• And, of course you need not do anything to prevent clients from seeing JSP tags; those tags are processed on the server and are not part of the output that is sent to the client.Confusing Translation Time with Request TimeA JSP page is converted into a servlet. The servlet is compiled, loaded into the server's memory, initialized, and executed. But which step happens when? To answer that question, remember two points:• The JSP page is translated into a servlet and compiled only the first time it is accessed after having been modified.• Loading into memory, initialization, and execution follow the normal rules for servlets.The most frequently misunderstood entries are highlighted. When referring to the table, note that servlets resulting from JSP pages use the _jspService method (called for both GET and POST requests), not doGet or doPost. Also, for initialization, they use the jspInit method, not the init method.JSP page translated into servlet Servlet compiled Servlet loaded into server's memory jspInit called _jspService called.4.What are application frameworks:A framework is a reusable, semi-complete application that can be specialized to produce custom applications [Johnson]. Like people, software applications are more alike than they are different. They run on the same computers, expect input from the same devices, output to the same displays, and save data to the same hard disks. Developers working on conventional desktop applications are accustomed to toolkits and development environments that leverage the sameness between applications. Application frameworks build on this common ground to provide developers with a reusable structure that can serve as the foundation for their own products.A framework provides developers with a set of backbone components that have the following characteristics:1.They are known to work well in other applications.2. They are ready to use with the next project.3. They can also be used by other teams in the organization.Frameworks are the classic build-versus-buy proposition. If you build it, you will understand it when you are done—but how long will it be before youcan roll your own? If you buy it, you will have to climb the learning curve—and how long is that going to take? There is no right answer here, but most observers would agree that frameworks such as Struts provide a significant return on investment compared to starting from scratch, especially for larger projects.Other types of frameworks:The idea of a framework applies not only to applications but to application componentsas well. Throughout this article, we introduce other types of frameworks that you can use with Struts. These include the Lucene search engine, the Scaffold toolkit, the Struts validator, and the Tiles tag library. Like application frameworks, these tools provide semi-complete versions of a subsystem that can be specialized to provide a custom component.Some frameworks have been linked to a proprietary development environment. This is not the case with Struts or any of the other frameworks shown in this book. You can use any development environment with Struts: Visual Age for Java, JBuilder, Eclipse, Emacs, and Textpad are all popular choices among Struts developers. If you can use it with Java, you can use it with Struts.Enabling technologies:Applications developed with Struts are based on a number of enabling technologies.These components are not specific to Struts and underlie every Java web application. A reason that developers use frameworks like Struts is to hide the nasty details behind acronyms like HTTP, CGI, and JSP. As a Struts developer, you don’t need to be an alphabet soup guru, but a working knowledge of these base technologies can help you devise creative solutions to tricky problems.Hypertext Transfer Protocol (HTTP):When mediating talks between nations, diplomats often follow a formal protocol.Diplomatic protocols are designed to avoid misunderstandings and to keep negotiations from breaking down. In a similar vein, when computers need to talk, they also follow a formal protocol. The protocol defines how data is transmitted and how to decode it once it arrives. Web applications use the Hypertext Transfer Protocol (HTTP) to move data between the browser running on your computer and the application running on the server.Many server applications communicate using protocols other than HTTP. Some of these maintain an ongoing connection between the computers. The application server knows exactly who is connected at all times and can tell when a connectionis dropped. Because they know the state of each connection and the identity of each person using it, these are known as stateful protocols.By contrast, HTTP is known as a stateless protocol. An HTTP server will accept any request from any client and will always provide some type of response, even if the response is just to say no. Without the overhead of negotiating and retaining a connection, stateless protocols can handle a large volume of requests. This is one reason why the Internet has been able to scale to millions of computers.Another reason HTTP has become the universal standard is its simplicity. An HTTP request looks like an ordinary text document. This has made it easy for applications to make HTTP requests. You can even send an HTTP request by hand using a standard utility such as Telnet. When the HTTP response comes back, it is also in plain text that developers can read.The first line in the HTTP request contains the method, followed by the locationof the requested resource and the version of HTTP. Zero or more HTTP request headers follow the initial line. The HTTP headers provide additional information to the server. This can include the browser type and version, acceptable document types, and the browser’s cookies, just to name a few. Of the seven request methods, GET and POST are by far the most popular.Once the server has received and serviced the request, it will issue an HTTP response. The first line in the response is called the status line and carries the HTTP protocol version, a numeric status, and a brief description of the status. Following the status line, the server will return a set of HTTP response headers that work in a way similar to the request headers.As we mentioned, HTTP does not preserve state information between requests.The server logs the request, sends the response, and goes blissfully on to the next request. While simple and efficient, a stateless protocol is problematic for dynamic applications that need to keep track of their users. (Ignorance is not always bliss.Cookies and URL rewriting are two common ways to keep track of users between requests. A cookie is a special packet of information on the user’s computer. URL rewriting stores a special reference in the page address that a Java server can use to track users. Neither approach is seamless, and using either means extra work when developing a web application. On its own, a standard HTTP web server does not traffic in dynamic content. It mainly uses the request to locatea file and then returns that file in the response. The file is typically formatted using Hypertext Markup Language (HTML) [W3C, HTML] that the web browser can format and display. The HTML page often includes hypertext links to other web pages and may display any number of other goodies, such as images and videos. The user clicks a link to make another request, and the process begins a new.Standard web servers handle static content and images quite well but need a helping hand to provide users with a customized, dynamic response.DEFINITION:Static content on the Web comes directly from text or data files, like HTML or JPEG files. These files might be changed from time to time, but they are not altered automatically when requested by a web browser. Dynamic content, on the other hand, is generated on the fly, typically in response to an individualized request from a browser.Common Gateway Interface (CGI):The first widely used standard for producing dynamic content was the Common Gateway Interface (CGI). CGI uses standard operating system features, such as environment variables and standard input and output, to create a bridge, or gateway, between the web server and other applications on the host machine. The other applications can look at the request sent to them by the web server and create a customized response.When a web serve r receives a request that’s intended for a CGI program, it runs that program and provides the program with information from the incoming request. The CGI program runs and sends its output back to the server. The web server then relays the response to the browser.CGI defines a set of conventions regarding what information it will pass as environment variables and how it expects standard input and output to be used. Like HTTP, CGI is flexible and easy to implement, and a great number of CGI-aware programs have been written.The main drawback to CGI is that it must run a new copy of the CGI-aware program for each request. This is a relatively expensive process that can bog down high-volume sites where thousands of requests are serviced per minute. Another drawback is that CGI programs tend to be platform dependent. A CGI program written for one operating system may not run on another.5. Java servlets:Sun’s Java Servlet platform directly addresses the two main drawbacks of CGI programs.First, servlets offer better performance and utilization ofresources than conventional CGI programs. Second, the write-once, run-anywhere nature of Java means that servlets are portable between operating systems that have a Java Virtual Machine (JVM).A servlet looks and feels like a miniature web server. It receives a request and renders a response. But, unlike conventional web servers, the servlet application programming interface (API) is specifically designed to help Java developers create dynamic applications.The servlet itself is simply a Java class that has been compiled into byte code, like any other Java object. The servlet has access to a rich API of HTTP-specific services, but it is still just another Java object running in an application and can leverage all your other Java assets.To give conventional web servers access to servlets, the servlets are plugged into containers. The servlet container is attached to the web server. Each servlet can declare what URL patterns it would like to handle. When a request matching a registered pattern arrives, the web server passes the request to the container, and the container invokes the servlet.But unlike CGI programs, a new servlet is not created for each request. Once the container instantiates the servlet, it will just create a new thread for each request. Java threads are much less expensive than the server processes used by CGI programs. Once the servlet has been created, using it for additional requests incurs very little overhead. Servlet developers can use the init() method to hold references to expensive resources, such as database connections or EJB Home Interfaces, so that they can be shared between requests. Acquiring resources like these can take several seconds—which is longer than many surfers are willing to wait.The other edge of the sword is that, since servlets are multithreaded, servlet developers must take special care to be sure their servlets are thread-safe. To learn more about servlet programming, we recommend Java Servlets by Example, by Alan R. Williamson [Williamson]. The definitive source for Servlet information is the Java Servlet Specification [Sun, JST].6. JavaServer Pages:While Java servlets are a big step up from CGI programs, they are not a panacea. To generate the response, developers are still stuck with using println statements to render the HTML. Code that looks like:out.println("<P>One line of HTML.</P>");out.println("<P>Another line of HTML.</P>");is all too common in servlets that generate the HTTP response. There are libraries that can help you generate HTML, but as applications grow more complex, Java developers end up being cast into the role of HTML page designers.Meanwhile, given the choice, most project managers prefer to divide development teams into specialized groups. They like HTML designers to be working on the presentation while Java engineers sweat the business logic. Using servlets alone encourages mixing markup with business logic, making it difficult for team members to specialize.To solve this problem, Sun turned to the idea of using server pages to combine scripting and templating technologies into a single component. To build Java Server Pages, developers start by creating HTML pages in the same old way, using the same old HTML syntax. To bring dynamic content into the page, the developer can also place JSP scripting elements on the page. Scripting elements are tags that encapsulate logic that is recognized by the JSP. You can easily pick out scripting elements on JSP pages by looking for code that begins with <% and ends with %>.To be seen as a JSP page, the file just needs to be saved with an extension of .jsp.When a client requests the JSP page, the container translates the page into a source code file for a Java servlet and compiles the source into a Java class file—just as you would do if you were writing a servlet from scratch. At runtime, the container can also check the last modified date of the JSP file against the class file. If the JSP file has changed since it was last compiled, the container will retranslate and rebuild the page all over again.Project managers can now assign the presentation layer to HTML developers, who then pass on their work to Java developers to complete the business-logic portion. The important thing to remember is that a JSP page is really just a servlet. Anything you can do with a servlet, you can do with a JSP.7. JavaBeans:JavaBeans are Java classes which conform to a set of design patterns that make them easier to use with development tools and other components.DEFINITION A JavaBean is a reusable software component written in Java. To qualify as a JavaBean, the class must be concrete and public, and have a noargument constructor. JavaBeans expose internal fields as properties byproviding public methods that follow a consistent design pattern. Knowing that the property names follow this pattern, other Java classes are able to use introspection to discover and manipulate JavaBean properties.The JavaBean design patterns provide access to the bean’s internal state through two flavor s of methods: accessors are used to read a JavaBean’s state; mutators are used to change a JavaBean’s state.Mutators are always prefixed with lowercase token set followed by the property name. The first character in the property name must be uppercase. The return value is always void—mutators only change property values; they do not retrieve them. The mutator for a simple property takes only one parameter in its signature, which can be of any type. Mutators are often nicknamed setters after their prefix. The mutator method signature for a weight property of the type Double would be:public void setWeight(Double weight)A similar design pattern is used to create the accessor method signature. Accessor methods are always prefixed with the lowercase token get, followed by the property name. The first character in the property name must be uppercase. The return value will match the method parameter in the corresponding mutator. Accessors for simple properties cannot accept parameters in their method signature. Not surprisingly, accessors are often called getters.The accessor method signature for our weight property is：public Double getWeight()If the accessor returns a logical value, there is a variant pattern. Instead of using the lowercase token get, a logical property can use the prefix is, followed by the property name. The first character in the property name must be uppercase. The return value will always be a logical value—either boolean or Boolean. Logical accessors cannot accept parameters in their method signature.The boolean accessor method signature for an on property would bepublic boolean isOn()The canonical method signatures play an important role when working with Java- Beans. Other components are able to use the Java Reflection API to discover a JavaBean’s properties by looking for methods prefixed by set, is, or get. If a component finds such a signature on a JavaBean, it knows that the method can be used to access or change the bean’s properties.。
THE TECHNIQUE DEVELOPMENT HISTORY OF JSPBy:Kathy Sierra and Bert BatesSource: Servlet&JSPThe Java Server Pages( JSP) is a kind of according to web of the script plait distance technique, similar carries the script language of Java in the server of the Netscape company of server- side JavaScript( SSJS) and the Active Server Pages(ASP) of the Microsoft. JSP compares the SSJS and ASP to have better can expand sex, and it is no more exclusive than any factory or some one particular server of Web. Though the norm of JSP is to be draw up by the Sun company of, any factory can carry out the JSP on own system.The After Sun release the JS P( the Java Server Pages) formally, the this kind of new Web application development technique very quickly caused the people's concern. JSP provided a special development environment for the Web application that establishes the high dynamic state. According to the Sun parlance, the JSP can adapt to include the Apache WebServer, IIS4.0 on the market at inside of 85% server product.This chapter will introduce the related knowledge of JSP and Databases, and JavaBean related contents.1.1 GENER ALIZEThe JSP(Java Server Pages) is from the company of Sun Microsystems initiate, the many companies the participate to the build up the together of the a kind the of dynamic the state web the page technique standard, the it have the it in the construction the of the dynamic state the web page the strong but the do not the especially of the function. JSP and the technique of ASP of the Microsoft is very alike. Both all provide the ability that mixes with a certain procedure code and is explain by thelanguage engine to carry out the procedure code in the code of HTML. Underneath we are simple of carry on the introduction to it.JSP pages are translated into servlets. So, fundamentally, any task JSP pages can perform could also be accomplished by servlets. However, this underlying equivalence does not mean that servlets and JSP pages are equally appropriate in all scenarios. The issue is not the power of the technology, it is the convenience, productivity, and maintainability of one or the other. After all, anything you can do on a particular computer platform in the Java programming language you could also do in assembly language. But it still matters which you choose.JSP provides the following benefits over servlets alone:• It is easier to write and maintain the HTML. Your static code is ordinary HTML: no extra backslashes, no double quotes, and no lurking Java syntax.• You can use standard Web-site development tools. Even HTML tools that know nothing about JSP can be used because they simply ignore the JSP tags.• You can divide up your development team. The Java programmers can work on the dynamic code. The Web developers can concentrate on the presentation layer. On large projects, this division is very important. Depending on the size of your team and the complexity of your project, you can enforce a weaker or stronger separation between the static HTML and the dynamic content.Now, this discussion is not to say that you should stop using servlets and use only JSP instead. By no means. Almost all projects will use both. For some requests in your project, you will use servlets. For others, you will use JSP. For still others, you will combine them with the MVC architecture . You want the apGFDGpropriate tool for the job, and servlets, by themselves, do not complete your toolkit.1.2 SOURCE OF JSPThe technique of JSP of the company of Sun, making the page of Webdevelop the personnel can use the HTML perhaps marking of XML to design to turn the end page with format. Use the perhaps small script future life of marking of JSP becomes the dynamic state on the page contents.( the contents changes according to the claim of)The Java Servlet is a technical foundation of JSP, and the large Web applies the development of the procedure to need the Java Servlet to match with with the JSP and then can complete, this name of Servlet comes from the Applet, the local translation method of now is a lot of, this book in order not to misconstruction, decide the direct adoption Servlet but don't do any translation, if reader would like to, can call it as" small service procedure". The Servlet is similar to traditional CGI, ISAPI, NSAPI etc. Web procedure development the function of the tool in fact, at use the Java Servlet hereafter, the customer need not use again he lowly method of CGI of efficiency, also need not use only the ability come to born page of Web of dynamic state in the method of API that a certain fixed Web server terrace circulate. Many servers of Web all support the Servlet, even not support the Servlet server of Web directly and can also pass the additional applied server and the mold pieces to support the Servlet. Receive benefit in the characteristic of the Java cross-platform, the Servlet is also a terrace irrelevant, actually, as long as match the norm of Java Servlet, the Servlet is complete to have nothing to do with terrace and is to have nothing to do with server of Web. Because the Java Servlet is internal to provide the service by the line distance, need not start a progress to the each claimses, and make use of the multi-threading mechanism can at the same time for several claim service, therefore the efficiency of Java Servlet is very high.But the Java Servlet also is not to has no weakness, similar to traditional CGI, ISAPI, the NSAPI method, the Java Servlet is to make use of to output the HTML language sentence to carry out the dynamic state web page of, if develop the whole website with the Java Servlet, the integration process of the dynamic state part and the static state pageis an evil-foreboding dream simply. For solving this kind of weakness of the Java Servlet, the SUN released the JSP.A number of years ago, Marty was invited to attend a small 20-person industry roundtable discussion on software technology. Sitting in the seat next to Marty was James Gosling, inventor of the Java programming language. Sitting several seats away was a high-level manager from a very large software company in Redmond, Washington. During the discussion, the moderator brought up the subject of Jini, which at that time was a new Java technology. The moderator asked the manager what he thought of it, and the manager responded that it was too early to tell, but that it seemed to be an excellent idea. He went on to say that they would keep an eye on it, and if it seemed to be catching on, they would follow his company's usual "embrace and extend" strategy. At this point, Gosling lightheartedly interjected "You mean disgrace and distend."Now, the grievance that Gosling was airing was that he felt that this company would take technology from other companies and suborn it for their own purposes. But guess what? The shoe is on the other foot here. The Java community did not invent the idea of designing pages as a mixture of static HTML and dynamic code marked with special tags. For example, Cold Fusion did it years earlier. Even ASP (a product from the very software company of the aforementioned manager) popularized this approach before JSP came along and decided to jump on the bandwagon. In fact, JSP not only adopted the general idea, it even used many of the same special tags as ASP did.The JSP is an establishment at the model of Java servlets on of the expression layer technique, it makes the plait write the HTML to become more simple.Be like the SSJS, it also allows you carry the static state HTML contents and servers the script mix to put together the born dynamic state exportation. JSP the script language that the Java is the tacit approval, however, be like the ASP and can use other languages( such as JavaScript and VBScript), the norm of JSP also allows to use other languages.1.3JSP CHARACTERISTICSIs a service according to the script language in some one language of the statures system this kind of discuss, the JSP should be see make is a kind of script language. However, be a kind of script language, the JSP seemed to be too strong again, almost can use all Javas in the JSP.Be a kind of according to text originally of, take manifestation as the central development technique, the JSP provided all advantages of the Java Servlet, and, when combine with a JavaBeans together, providing a kind of make contents and manifestation that simple way that logic separate. Separate the contents and advantage of logical manifestations is, the personnel who renews the page external appearance need not know the code of Java, and renew the JavaBeans personnel also need not be design the web page of expert in hand, can use to take the page of JavaBeans JSP to define the template of Web, to build up a from have the alike external appearance of the website that page constitute. JavaBeans completes the data to provide, having no code of Java in the template thus, this means that these templates can be written the personnel by a HTML plait to support. Certainly, can also make use of the Java Servlet to control the logic of the website, adjust through the Java Servlet to use the way of the document of JSP to separate website of logic and contents.Generally speaking, in actual engine of JSP, the page of JSP is the edit and translate type while carry out, not explain the type of. Explain the dynamic state web page development tool of the type, such as ASP, PHP3 etc., because speed etc. reason, have already can't satisfy current the large electronic commerce needs appliedly, traditional development techniques are all at to edit and translate the executive way change, such as the ASP → ASP+;PHP3 → PHP4.In the JSP norm book, did not request the procedure in the JSP code part( be called the Scriptlet) and must write with the Java definitely. Actually, have some engines of JSP are adoptive other script languages such as the EMAC- Script, etc., but actually this a few script languagesalso are to set up on the Java, edit and translate for the Servlet to carry out of. Write according to the norm of JSP, have no Scriptlet of relation with Java also is can of, however, mainly lie in the ability and JavaBeans, the Enterprise JavaBeanses because of the JSP strong function to work together, so even is the Scriptlet part not to use the Java, edit and translate of performance code also should is related with Java.1.4JSP MECHANISMTo comprehend the JSP how unite the technical advantage that above various speak of, come to carry out various result easily, the customer must understand the differentiation of" the module develops for the web page of the center" and" the page develops for the web page of the center" first.The SSJS and ASP are all in several year ago to release, the network of that time is still very young, no one knows to still have in addition to making all business, datas and the expression logic enter the original web page entirely heap what better solve the method. This kind of model that take page as the center studies and gets the very fast development easily. However, along with change of time, the people know that this kind of method is unwell in set up large, the Web that can upgrade applies the procedure. The expression logic write in the script environment was lock in the page, only passing to shear to slice and glue to stick then can drive heavy use. Express the logic to usually mix together with business and the data logics, when this makes be the procedure member to try to change an external appearance that applies the procedure but do not want to break with its llied business logic, apply the procedure of maintenance be like to walk the similar difficulty on the eggshell. In fact in the business enterprise, heavy use the application of the module already through very mature, no one would like to rewrite those logics for their applied procedure.HTML and sketch the designer handed over to the implement work of their design the Web plait the one who write, make they have to double work- Usually is the handicraft plait to write, becausehave no fit tool and can carry the script and the HTML contents knot to the server to put together. Chien but speech, apply the complexity of the procedure along with the Web to promote continuously, the development method that take page as the center limits sex to become to get up obviously.At the same time, the people always at look for the better method of build up the Web application procedure, the module spreads in customer's machine/ server the realm. JavaBeans and ActiveX were published the company to expand to apply the procedure developer for Java and Windows to use to come to develop the complicated procedure quickly by" the fast application procedure development"( RAD) tool. These techniques make the expert in the some realm be able to write the module for the perpendicular application plait in the skill area, but the developer can go fetch the usage directly but need not control the expertise of this realm.Be a kind of take module as the central development terrace, the JSP appeared. It with the JavaBeans and Enterprise JavaBeans( EJB) module includes the model of the business and the data logic for foundation, provide a great deal of label and a script terraces to use to come to show in the HTML page from the contents of JavaBeans creation or send a present in return. Because of the property that regards the module as the center of the JSP, it can drive Java and not the developer of Java uses equally. Not the developer of Java can pass the JSP label( Tags) to use the JavaBeans that the deluxe developer of Java establish. The developer of Java not only can establish and use the JavaBeans, but also can use the language of Java to come to control more accurately in the JSP page according to the expression logic of the first floor JavaBeans.See now how JSP is handle claim of HTTP. In basic claim model, a claim directly was send to JSP page in. The code of JSP controls to carry on hour of the logic processing and module of JavaBeanses' hand over with each other, and the manifestation result in dynamic state bornly, mixing with the HTML page of the static state HTML code. The Beans can be JavaBeansor module of EJBs. Moreover, the more complicated claim model can see make from is request other JSP pages of the page call sign or Java Servlets.The engine of JSP wants to chase the code of Java that the label of JSP, code of Java in the JSP page even all converts into the big piece together with the static state HTML contents actually. These codes piece was organized the Java Servlet that customer can not see to go to by the engine of JSP, then the Servlet edits and translate them automatically byte code of Java.Thus, the visitant that is the website requests a JSP page, under the condition of it is not knowing, an already born, the Servlet actual full general that prepared to edit and translate completes all works, very concealment but again and efficiently. The Servlet is to edit and translate of, so the code of JSP in the web page does not need when the every time requests that page is explain. The engine of JSP need to be edit and translate after Servlet the code end is modify only once, then this Servlet that editted and translate can be carry out. The in view of the fact JSP engine auto is born to edit and translate the Servlet also, need not procedure member begins to edit and translate the code, so the JSP can bring vivid sex that function and fast developments need that you are efficiently.Compared with the traditional CGI, the JSP has the equal advantage. First, on the speed, the traditional procedure of CGI needs to use the standard importation of the system to output the equipments to carry out the dynamic state web page born, but the JSP is direct is mutually the connection with server. And say for the CGI, each interview needs to add to add a progress to handle, the progress build up and destroy by burning constantly and will be a not small burden for calculator of be the server of Web. The next in order, the JSP is specialized to develop but design for the Web of, its purpose is for building up according to the Web applied procedure, included the norm and the tool of a the whole set. Use the technique of JSP can combine a lot of JSP pages to become a Web applicationprocedure very expediently.1.5 The operation principle and the advantages of JSP tagsIn this section of the operating principle of simple introduction JSP and strengths.For the first time in a JSP documents requested by the engine, JSP Servlet is transformed into a document JSP. This engine is itself a Servlet. The operating process of the JSP shown below:(1) the JSP engine put the JSP files converting a Java source files (Servlet), if you find the files have any grammar mistake JSP, conversion process will interrupt, and to the server and client output error messages.(2) if converted, with the engine JSP javac Java source file compiler into a corresponding scale-up files.(3) to create a the Servlet (JSP page), the transformation of the Servlet jspInit () method was executed, jspInit () method in the life cycle of Servlet executed only once.(4) jspService () method invocation to the client requests. For each request, JSP engine to create a new thread for processing the request. If you have multiple clients and request the JSP files, JSP engine will create multiple threads. Each client requests a thread. To execute multi-thread can greatly reduce the requirement of system resources, improving the concurrency value and response time. But also should notice the multi-thread programming, due to the limited Servlet always in response to memory, so is very fast.(5) if the file has been modified. The JSP, server will be set according to the document to decide whether to recompile, if need to recompile, will replace the Servlet compile the memory and continue the process.(6) although the JSP efficiency is high, but at first when the need to convert and compile and some slight delay. In addition, if at any time due to reasons of system resources, JSP engine will in some way ofuncertain Servlet will remove from memory. When this happens jspDestroy () method was first call.(7) and then Servlet examples were marked with "add" garbage collection. But in jspInit () some initialization work, if establish connection with database, or to establish a network connection, from a configuration file take some parameters, such as, in jspDestory () release of the corresponding resources.Based on a Java language has many other techniques JSP page dynamic characteristics, technical have embodied in the following aspects: One simplicity and effectivenessThe JSP dynamic web pages with the compilation of the static HTML pages of writing is very similar. Just in the original HTML page add JSP tags, or some of the proprietary scripting (this is not necessary). So, a familiar with HTML page write design personnel may be easily performed JSP page development. And the developers can not only, and write script by JSP tags used exclusively others have written parts to realize dynamic pages. So, an unfamiliar with the web developers scripting language, can use the JSP make beautiful dynamic pages. And this in other dynamic web development is impossible.Tow the independence of the programThe JSP are part of the family of the API Java, it has the general characteristics of the cross-platform Java program. In other words, is to have the procedure, namely the independence of the platform, 6 Write bided anywhere! .Three procedures compatibilityThe dynamic content can various JSP form, so it can show for all kinds of customers, namely from using HTML/DHTML browser to use various handheld wireless equipment WML (for example, mobile phones and pdas), personal digital equipment to use XML applications, all can use B2B JSP dynamic pages.Four program reusabilityIn the JSP page can not directly, but embedded scripting dynamic interaction will be cited as a component part. So, once such a component to write, it can be repeated several procedures, the program of the reusability. Now, a lot of standard JavaBeans library is a good example.JSP的技术发展历史作者： Kathy Sierra and Bert Bates来源： Servlet&JSPJava Server Pages(JSP)是一种基于web的脚本编程技术，类似于网景公司的服务器端Java脚本语言——server-side JavaScript(SSJS)和微软的Active Server Pages(ASP).与SSJS和ASP相比，JSP具有更好的可扩展性，并且它不专属于任何一家厂商或某一特定的Web服务器。
JSP的技术发展历史作者：Kathy Sierra and Bert Bates来源：Servlet&JSPJava Server Page(JSP)是一种基于web脚本的编译技术，类似于Notespace 公司服务器端的Java脚本语言--server- side JavaScript(SSJS)和微软公司的Active Server Pages(ASP)。
JSP相较于SSJS和ASP具有更好的扩展性，并且它不专属于任何一家厂商或某一特定的Web服务器。
尽管JSP的规范是由SUN公司制定的，但是任何一家厂商都可以在自己的系统上进行JSP的开发。
SUN公司正式推出JSP（Java Server Page)之后，这种新的Web应用开发技术很快引起了人们的关注。
JSP为高度动态的Web应用提供了一个特殊的开发环境。
根据SUN公司的说法，JSP适用于包括Apache Web服务器、IIS4.0 等85%的市场现有的服务器产品。
这一章将介绍JSP和Databases相关知识，以及JavaBean的相关内容，当然仅仅是些基础内容的介绍，可以说只是个引导，如果读者需要了解更详细的内容，请查阅JSP的相关书籍。
1.1概要JSP始发于SUN Microsystems公司，很多公司参与建立的一种动态web页面技术标准，它在动态web页面中具有强大但不独特的功能。
JSP与微软公司的ASP技术非常相似。
它们都提供了在HTML页面中掺入程序代码并且由语言引擎阐述的功能。
下面，我们简单的介绍一下。
JSP页面是由servlet演化而来的。
因此，基本上，任何JSP页面能进行的任务都可以由servlet实现。
然而，基础相等的意思并不是说servlet和JSP页面在所有的情况下都有相同的功效。
问题并不在于技术层面，而是在于两者在便利性、效率和可维护性方面的差异。
毕竟，任何你可以在特定计算机平台上用Java编程语言完成的东西，都可以用汇编语言完成。
附录A中文译文Jsp技术介绍JSP（JA V A SERVER PAGES）是由Sun Microsystems 公司倡导、许多公司参与一起建立的一种动态网页技术标准，其在动态网页的建设中有其强大而特别的功能，他主要用于创建可支持跨平台及跨Web服务器的动态网页。
JSP可与微软的Active Server Pages (ASP)相媲美，但JSP使用的是类似于HTML的标记和Java 代码片段而不是用VBScript。
当你使用不提供ASP本地支持的Web服务器（例如Apache或Netscape服务器）时，你就可以考虑使用JSP了。
Java Server Pages技术可以让web开发人员和设计人员非常容易的创建和维护动态网页，特别是目前的商业系统。
作为JavaTM技术的一部分，JSP能够快速开发出基于web独立平台的应用程序。
JSP 把用户界面从系统内容中分离开来，使得设计人员能够在不改变底层动态内容的前提下改变整个网页布局。
那么什么是Java Server Page呢?简单的说，一个JSP网页就是在HTML网页中包含了能够生成动态内容的可执行应用程序代码。
此应用程序可能包含JavaBeanTM，JDBCTM对象，Enterprise Java BeanTM (E J B )和Remote Method Invocation (RMI)对象，所有的部分都可以非常容易的从JSP网页上访问到。
例如，一个JSP网页可以包含HTML代码所显示的静态文本和图像，也可以调用一个JDBC对象来访问数据库；当网页显示到用户界面上以后，它将包含静态HTML内容和从数据库中找到相应的动态信息。
在JSP网页中，要把用户界面和应用程序分开可以考虑在网页设计人员和开发人员之间执行一个非常方便的授权任务。
它也允许开发人员去建立灵活的代码，从而非常容易的进行更新和重复利用。
由于JSP网页能够根据需要自动进行编译，web设计人员无须重新编译应用程序逻辑就可以改变表述代码。
Servlet程序在服务器端运行，动态地生成Web页面与传统的CGI和许多其他类似CGI的技术相比，Java Servlet具有更高的效率，更容易使用，功能更强大，具有更好的可移植性，更节省投资。
Servlet是运行在Web或应用服务器上的Java程序，它是一个中间层，负责连接来自Web浏览器或其他HTTP客户程序的请求和HTTP服务器上的数据库或应用程序。
最终用户一般在页面的HTML表单中输入这些数据。
然而，数据还有可能来自applet或定制的HTTP客户程序。
实际上从客户端传送到Web服务器的数据有两种，它们分别为用户在表单中输入的显式数据，以及后台的HTTP信息。
两种数据都很重要。
HTTP信息包括cookie、浏览器所能识别的媒体类型和压缩模式等。
这个过程可能需要访问数据库、执行RMI或EJB调用、调用Web服务，或者直接计算得出对应的响应。
实际的数据可能存储在关系型数据库中。
该数据库可能不理解HTTP，或者不能返回HTML形式的结果，所有Web浏览器不能直接与数据库进行会话。
即使它能够做到这一点，为了安全上的考虑，我们也不希望让它这么做。
对应大多数其他应用程序，也存在类似的问题。
因此，我们需要Web 中间层从HTTP流中提取输入数据，与应用程序会话，并将结果嵌入到文档中。
这个文档可以用各种格式发送，包括文本（HTML或XML），二进制（GIF图），甚至可以式建立在其他底层格式之上的压缩格式，如gzip。
但是，到目前为止，HTML式最常用的格式，故而servelt和JSP的重要任务之一就式将结果包装到HTML中。
实际发送的数据有两种：文档本身，以及后台的HTTP信息。
同样，两种数据对开发来说都式至关重要的。
HTTP响应数据的发送过程涉及告知浏览器或其他客户程序所返回文档的类型（如HTML），设置cookie和缓存参数，以及其他类似的任务。
预先建立的文档可以满足客户的许多请求，服务器无需调用servlet就可以处理这些请求。
毕业设计（论文）外文文献翻译文献、资料中文题目：SP及其WEB技术文献、资料英文题目：文献、资料来源：文献、资料发表（出版）日期：院（部）：专业：班级：姓名：学号：指导教师：翻译日期： 2017.02.14外文翻译原文及译文JSP and WEB technolog1 JSP IntroductionJSP (JavaServer Pages) is a Java-based scripting technology. Is advocated by Sun Microsystems Inc., together with a number of companies involved in the establishment of a dynamic web page technology standards. JSP technology is somewhat similar to ASP technology, It is a traditional HTML page file (*. htm, *. html) to insert Java program segment (Scriptlet) and JSP tag (tag), To form the JSP file（*jsp）. Web development with JSP is a cross-platform applications that can run under Linux, but also in other operating systems. In the JSP of the many advantages, one of which is that it will be HTML encoded Web page from the business logic separated effectively. JSP access with reusable components, such as Servlet, JavaBean and Java-based Web applications. JSP also supports directly in the Web page embedded Java code. JSP can be used two ways to access documents: JSP documents sent by the browser request, the request sent to the Servlet. JSP technology uses Java programming language, XML-type tags and scriptlets, to have a package deal with the logic of dynamic pages. Page tags and scriptlets can also exist in the server access to the resources of the application logic. JSP logic and Web page design and display isolated and support reusable component-based design, Web-based applications more quickly and easily developed.The Web server when meets visits the JSP homepage the request, first carries out segment, will then carry out the result code to return together with JSP in the document HTML for the customer. The insertion Java segment may operate the database, again the directional homepage and so on, realizes the function which the establishment dynamic homepage needs. JSP and Java Servlet are the same, is in the server end execution, usually returns to this client side is a HTML text, therefore client side, so long as has the browser to be able to glance over.The JSP page is composed of the HTML code and the inserting Java code. The server in the page by the client side was requested that later will carry on processing to these Java code, will then produce the HTML page will return gives the client side thebrowser. Java Servlet is the JSP technology base, moreover the large-scale Web application procedure's development needs Java Servlet and the JSP coordination can complete. JSP had the Java technology simply easy to use, complete object-oriented, had the platform independency, and safe reliable, mainly faced Internet's all characteristics.2 JSP computing techniqueTo carry on the dynamic website conveniently fast the development, JSP has made the improvement in the following several aspects, causes it to become builds the cross platform fast the dynamic website first choice plan.2.1 carries on the content production and the demonstration separatesWith the JSP technology, the Web page development personnel may use HTML or the XML marking design and the formatted final page, and uses the JSP marking or the tootsy produces on page's dynamic content originally. Production content's logic is sealed in marks and in the JavaBeans module, and ties up in the script, all scripts in server end movement. Because core logic is sealed in marks and in JavaBeans, therefore the Web administrative personnels and the page designer, can edit and use the JSP page, but does not affect the content the production. In the server end, the JSP engine explained that the JSP marking and the script, produce the content which requested, and (or XML) page's form transmits the result by HTML the browser. This both are helpful in the author protects own code, and can guarantee any based on the HTML Web browser's complete usability.2.2 may entrust with heavy responsibility the moduleThe overwhelming majority JSP page relies on may entrust with heavy responsibility, the cross platform module (JavaBeans or Enterprise the JavaBeans module) carries out complex processing which the application procedure requests. The development personnel can share and exchange the execution ordinary operation the module, or causes these modules uses for more users and the customer association. Has accelerated the overall development process based on module's method, and causes each kind of organization obtains balanced in their existing skill and in the optimized result development endeavor.2.3 uses markingThe Web page development personnel will not be the familiar script languageprogrammers. The JSP technology has sealed many functions, these functions are easy to use, marking to carry on the dynamic content production with JSP in the related XML to need. The standard JSP marking can visit and the instantiation JavaBeans module, the establishment or the retrieval module attribute, downloads Applet, as well as the execution difficulty with codes and the time-consuming function with other methods.2.4 adapts the platformNearly all platforms support Java, JSP+JavaBeans to be possible to pass unimpeded nearly under all platforms. Transplants from a platform to other platform, JSP and JavaBeans does not even need to translate, because the Java byte code is standard has nothing to do with the platform.2.5 database connectionIn Java connects the database the technology is the JDBC, Java procedure is connected through the JDBC driver and the database, operations and so on execution inquiry, extraction data. Sun Corporation has also developed JDBC-ODBC bridge, uses this technical Java procedure to be possible to visit has the ODBC driver database, at present the majority database systems have the ODBC driver, therefore the Java procedure can visit such as Oracle, Sybase, MS SQL Server and databases and so on MS Access. In addition, through the development marking storehouse, the JSP technology may further expand. The third party development personnel and other personnel may found their marking storehouse for the commonly used function. This enables the Web page development personnel to be able to use the familiar tool and to be similar to marking same carries out the specific function component to carry on the work. The JSP technology very easy conformity to many kinds of application architecture, to use the extant tool and the skill, and can expand to the support enterprise distributional application.3 Eclipse function synopsisMore and more Java development personnel already started the productivity which and the quality income appreciates Eclipse JDT to provide. It was the Java editor provides grammar Gao Liang to demonstrate that the formatting, the fold, the content were auxiliary, code template and so on many functions. It grows unceasingly available restructuring and the code generation function set permits you in a higher rank the operation code, andautomated usual code intensity duty and easy wrong duty. Moreover, in develops the code and uses JDT to compile and to carry out the JUnit test built-in support carries on the unit testing after the code, may use Eclipse the first-class Java debugger debugging when the movement meets any question. Besides JDT, Eclipse SDK- the most popular downloading - also contains Plug-in Development Environment(PDE). PDE used the specific function to expand JDT to construct the Eclipse plug-in unit - based on the Eclipse application procedure basic construction agglomeration. In fact, uses the tool which provides by Eclipse itself to be able to surmount the Java development, may expand the existing Eclipse application procedure, or even founds the brand-new application procedure.Eclipse by a script level constitution, contains in many functional modules or the Eclipse terminology so-called “the plug-in unit”. The plug-in unit is provides all functions in the Eclipse application procedure the module. They cooperate through its API to pay the final outcome together. In Eclipse, even the most foundation's function, for instance the search and the start installment's plug-in unit, seals in the plug-in unit. In order to expand the existing Eclipse function or carry on the construction in above, the plug-in unit the concrete expansion contribution for the expansion spot which will expose by other plug-in units. Usually, the plug-in unit concentrates the specific region responsibility, and gives through or a many expansion way other responsibility designation other plug-in units. For example, a plug-in unit allows you parallel to compare two documents visibly the contents, but it will not care how to read these documents even how to explain these document structure; This is other plug-in unit's work. When compared with two documents, this plug-in unit first inspects whether to have another plug-in unit to be possible to explain these document structure. If found one, it to the plug-in unit inquiry related file organization information which found, and used this information in the comparison process.May see that the modular construction was Eclipse has provided the huge flexibility, and provided one to be possible to support the massive application procedure platform which the original design has not expected.4 Structs function synopsisStruts is a MVC frame (Framework), uses in developing Java fast the Web application.Struts realizes the key point in C(Controller), Action which and we have custom-made including ActionServlet/RequestProcessor, was also V(View) provides a series of rows to have custom-made the label (Custom Tag). Spring is a light vessel (light-weight container), its core is the Bean factory (Bean Factory), with constructs M(Model) which we need. Above this foundation, Spring has provided AOP (Aspect-Oriented Programming, face stratification plane programming) realization, provides under the non-management environment with it to declare services and so on way business, security; Is more convenient to Bean factory expansion ApplicationContext we to realize the J2EE application; DAO/ORM realizes facilitates us to carry on the database the development; Web MVC and Spring Web have provided Java the Web application frame or carries on the integration with other popular Web frame. That is may a both use, achieve both own characteristic carries on supplementary.Structs is the kind which, servlet and the JSP mark a group cooperates mutually, they compose the MVC 2 designs which may entrust with heavy responsibility. This definition expressed that Struts is a frame, but is not a storehouse, but Struts has also contained the rich mark storehouse and the independence in this frame work utility program class.Client browser (customer browser), the request founds an event from customer browser's each HTTP. The Web vessel will use a HTTP response to make the response.Controller (controller), the controller receive from browser's request, and decided that sends out where this request. Speaking of Struts, the controller is an order design pattern which realizes by servlet. struts-config.xml document disposition controller.Service logic, the service logic renewal model's condition, and helps the control application procedure the flow. Speaking of Struts, this is through takes the actual service logic “thin” the packing Action kind to complete.Model (model) condition, model expression application procedure condition. Service object renewal application procedure condition. ActionForm bean in conversation level or request level expression model condition, but is not in the lasting level. The JSP document uses JSP to mark the read from the ActionForm bean information.View (view), the view is a JSP document. And does not have the flow logic, does not have the service logic, also does not have the model information -- Only then marks. The mark causes Struts is different with other frames (for example Velocity) one of factors.Just like the Struts controller is (event usually is HTTP post) maps the event kind of。
外文翻译原文及译文学院计算机学院专业计算机科学与技术班级学号姓名指导教师负责教师JSP and WEB technolog1 JSP IntroductionJSP (JavaServer Pages) is a Java-based scripting technology. Is advocated by Sun Microsystems Inc., together with a number of companies involved in the establishment of a dynamic web page technology standards. JSP technology is somewhat similar to ASP technology, It is a traditional HTML page file (*. htm, *. html) to insert Java program segment (Scriptlet) and JSP tag (tag), To form the JSP file（*jsp）. Web development with JSP is a cross-platform applications that can run under Linux, but also in other operating systems. In the JSP of the many advantages, one of which is that it will be HTML encoded Web page from the business logic separated effectively. JSP access with reusable components, such as Servlet, JavaBean and Java-based Web applications. JSP also supports directly in the Web page embedded Java code. JSP can be used two ways to access documents: JSP documents sent by the browser request, the request sent to the Servlet. JSP technology uses Java programming language, XML-type tags and scriptlets, to have a package deal with the logic of dynamic pages. Page tags and scriptlets can also exist in the server access to the resources of the application logic. JSP logic and Web page design and display isolated and support reusable component-based design, Web-based applications more quickly and easily developed.The Web server when meets visits the JSP homepage the request, first carries out segment, will then carry out the result code to return together with JSP in the document HTML for the customer. The insertion Java segment may operate the database, again the directional homepage and so on, realizes the function which the establishment dynamic homepage needs. JSP and Java Servlet are the same, is in the server end execution, usually returns to this client side is a HTML text, therefore client side, so long as has the browser to be able to glance over.The JSP page is composed of the HTML code and the inserting Java code. The server in the page by the client side was requested that later will carry on processing to these Java code, will then produce the HTML page will return gives the client side the browser. Java Servlet is the JSP technology base, moreover the large-scale Web applicationprocedure's development needs Java Servlet and the JSP coordination can complete. JSP had the Java technology simply easy to use, complete object-oriented, had the platform independency, and safe reliable, mainly faced Internet's all characteristics.2 JSP computing techniqueTo carry on the dynamic website conveniently fast the development, JSP has made the improvement in the following several aspects, causes it to become builds the cross platform fast the dynamic website first choice plan.2.1 carries on the content production and the demonstration separatesWith the JSP technology, the Web page development personnel may use HTML or the XML marking design and the formatted final page, and uses the JSP marking or the tootsy produces on page's dynamic content originally. Production content's logic is sealed in marks and in the JavaBeans module, and ties up in the script, all scripts in server end movement. Because core logic is sealed in marks and in JavaBeans, therefore the Web administrative personnels and the page designer, can edit and use the JSP page, but does not affect the content the production. In the server end, the JSP engine explained that the JSP marking and the script, produce the content which requested, and (or XML) page's form transmits the result by HTML the browser. This both are helpful in the author protects own code, and can guarantee any based on the HTML Web browser's complete usability.2.2 may entrust with heavy responsibility the moduleThe overwhelming majority JSP page relies on may entrust with heavy responsibility, the cross platform module (JavaBeans or Enterprise the JavaBeans module) carries out complex processing which the application procedure requests. The development personnel can share and exchange the execution ordinary operation the module, or causes these modules uses for more users and the customer association. Has accelerated the overall development process based on module's method, and causes each kind of organization obtains balanced in their existing skill and in the optimized result development endeavor.2.3 uses markingThe Web page development personnel will not be the familiar script language programmers. The JSP technology has sealed many functions, these functions are easy touse, marking to carry on the dynamic content production with JSP in the related XML to need. The standard JSP marking can visit and the instantiation JavaBeans module, the establishment or the retrieval module attribute, downloads Applet, as well as the execution difficulty with codes and the time-consuming function with other methods.2.4 adapts the platformNearly all platforms support Java, JSP+JavaBeans to be possible to pass unimpeded nearly under all platforms. Transplants from a platform to other platform, JSP and JavaBeans does not even need to translate, because the Java byte code is standard has nothing to do with the platform.2.5 database connectionIn Java connects the database the technology is the JDBC, Java procedure is connected through the JDBC driver and the database, operations and so on execution inquiry, extraction data. Sun Corporation has also developed JDBC-ODBC bridge, uses this technical Java procedure to be possible to visit has the ODBC driver database, at present the majority database systems have the ODBC driver, therefore the Java procedure can visit such as Oracle, Sybase, MS SQL Server and databases and so on MS Access. In addition, through the development marking storehouse, the JSP technology may further expand. The third party development personnel and other personnel may found their marking storehouse for the commonly used function. This enables the Web page development personnel to be able to use the familiar tool and to be similar to marking same carries out the specific function component to carry on the work. The JSP technology very easy conformity to many kinds of application architecture, to use the extant tool and the skill, and can expand to the support enterprise distributional application.3 Eclipse function synopsisMore and more Java development personnel already started the productivity which and the quality income appreciates Eclipse JDT to provide. It was the Java editor provides grammar Gao Liang to demonstrate that the formatting, the fold, the content were auxiliary, code template and so on many functions. It grows unceasingly available restructuring and the code generation function set permits you in a higher rank the operation code, and automated usual code intensity duty and easy wrong duty. Moreover, in develops the codeand uses JDT to compile and to carry out the JUnit test built-in support carries on the unit testing after the code, may use Eclipse the first-class Java debugger debugging when the movement meets any question. Besides JDT, Eclipse SDK- the most popular downloading - also contains Plug-in Development Environment(PDE). PDE used the specific function to expand JDT to construct the Eclipse plug-in unit - based on the Eclipse application procedure basic construction agglomeration. In fact, uses the tool which provides by Eclipse itself to be able to surmount the Java development, may expand the existing Eclipse application procedure, or even founds the brand-new application procedure.Eclipse by a script level constitution, contains in many functional modules or the Eclipse terminology so-called “the plug-in unit”. The plug-in unit is provides all functions in the Eclipse application procedure the module. They cooperate through its API to pay the final outcome together. In Eclipse, even the most foundation's function, for instance the search and the start installment's plug-in unit, seals in the plug-in unit. In order to expand the existing Eclipse function or carry on the construction in above, the plug-in unit the concrete expansion contribution for the expansion spot which will expose by other plug-in units. Usually, the plug-in unit concentrates the specific region responsibility, and gives through or a many expansion way other responsibility designation other plug-in units. For example, a plug-in unit allows you parallel to compare two documents visibly the contents, but it will not care how to read these documents even how to explain these document structure; This is other plug-in unit's work. When compared with two documents, this plug-in unit first inspects whether to have another plug-in unit to be possible to explain these document structure. If found one, it to the plug-in unit inquiry related file organization information which found, and used this information in the comparison process.May see that the modular construction was Eclipse has provided the huge flexibility, and provided one to be possible to support the massive application procedure platform which the original design has not expected.4 Structs function synopsisStruts is a MVC frame (Framework), uses in developing Java fast the Web application. Struts realizes the key point in C(Controller), Action which and we have custom-madeincluding ActionServlet/RequestProcessor, was also V(View) provides a series of rows to have custom-made the label (Custom Tag). Spring is a light vessel (light-weight container), its core is the Bean factory (Bean Factory), with constructs M(Model) which we need. Above this foundation, Spring has provided AOP (Aspect-Oriented Programming, face stratification plane programming) realization, provides under the non-management environment with it to declare services and so on way business, security; Is more convenient to Bean factory expansion ApplicationContext we to realize the J2EE application; DAO/ORM realizes facilitates us to carry on the database the development; Web MVC and Spring Web have provided Java the Web application frame or carries on the integration with other popular Web frame. That is may a both use, achieve both own characteristic carries on supplementary.Structs is the kind which, servlet and the JSP mark a group cooperates mutually, they compose the MVC 2 designs which may entrust with heavy responsibility. This definition expressed that Struts is a frame, but is not a storehouse, but Struts has also contained the rich mark storehouse and the independence in this frame work utility program class.Client browser (customer browser), the request founds an event from customer browser's each HTTP. The Web vessel will use a HTTP response to make the response.Controller (controller), the controller receive from browser's request, and decided that sends out where this request. Speaking of Struts, the controller is an order design pattern which realizes by servlet. struts-config.xml document disposition controller.Service logic, the service logic renewal model's condition, and helps the control application procedure the flow. Speaking of Struts, this is through takes the actual service logic “thin” the packing Action kind to complete.Model (model) condition, model expression application procedure condition. Service object renewal application procedure condition. ActionForm bean in conversation level or request level expression model condition, but is not in the lasting level. The JSP document uses JSP to mark the read from the ActionForm bean information.View (view), the view is a JSP document. And does not have the flow logic, does not have the service logic, also does not have the model information -- Only then marks. The mark causes Struts is different with other frames (for example Velocity) one of factors.Just like the Struts controller is (event usually is HTTP post) maps the event kind of servlet. you to expect - the air-operated controller use configuration files to cause you notto need to carry on to these values the hard code. The time has changed, but method as before.The Action kind, ActionForm maintains the Web application procedure the conversation condition. ActionForm is one abstract class, must found this kind of subclass for each input form model. When I said when input form model, what refers to the ActionForm expression is establishes or in the renewal general sense data by the HTML form.The Action kind is service logic packing. A Action kind of use is transforms HttpServletRequest into the service logic. Must use Action, please found its subclass and covers process () the method.ActionServlet (Command) will use perform () the method the parametrization kind to transmit for ActionForm. Still did not have too many repugnant request.getParameter () to transfer. When the event progresses to this step, the input form data (or HTML form data) has been withdrawn from the request class and shifts to the ActionForm kind.Considered that a Action kind of another way is the Adapter design pattern. The Action use will be “a kind of connection will transform another connection which will need for the client. Adapter enables the kind the joint operation, if does not have Adapter, then these kinds will be unable because of the incompatible connection the joint operation.”. In this example's client is ActionServlet, it knows nothing about to our concrete service class connection. Therefore, Struts has provided a service connection which it can understand, namely Action. Through expands Action, we cause our service connection and the Struts service connection maintain compatible.5 CSS synopsisThe CSS edition method is the same with HTML, may also be any text editor or the homepage edition software, but also has uses for to edit CSS specially the software. If you write the CSS sentence regards the exterior cascading style sheet, but transfers in the HTML document, then its extension saves .css to be possible. Initially the technical personnel found out HTML, mainly stresses on the definition content, for instance expressed that a paragraph, indicates the title, but excessively has not designed HTML the typesetting and the contact surface effect.Along with the Internet rapid development, HTML is widely applied, the surfer people hoped certainly that the homepage makes attractive, therefore the HTMLtypesetting and the contact surface effect's limitation exposes day by day. In order to solve this problem, the people also took many tortuous paths, has used some not good method, for instance increases many attribute results to HTML becomes the code very extremely fat, turns the picture the text, excessively many comes the typesetting using Table, expresses the white space with the blank picture and so on. Appears until CSS.CSS may be a homepage design breakthrough, it has solved the homepage contact surface typesetting difficult problem. May such say that HTML Tag is mainly defines the homepage content (Content), but CSS decided how these homepage content does demonstrate (Layout). The CSS English is Cascading Style Sheets, Chinese may translate the tandem cascading style sheet. CSS may divide into three kinds according to its position: In inlays the style (Inline Style), internal cascading style sheet (Internal Style Sheet), exterior cascading style sheet (External Style Sheet).6 HTML function synopsisHyper Text Markup the Language hypertext mark language is one kind uses for to manufacture the hypertext documents the simple mark language. The hypertext documents which compiles with HTML are called the HTML documents, it can the independence in each kind of operating system platform (for example UNIX, WINDOWS and so on). HTML has served as since 1990 on World Wide Web the information to express the language, uses in describing the Homepage form design and it and on WWW the other Homepage linked information.The HTML documents (i.e. the Homepage source document) was one has laid aside the mark ASCII text document, usually it had .html or the .htm document extension. Produces HTML documents mainly to have the following three ways: 1. the manual direct compilation (e.g. ASCII text editor which or other HTML edition tool likes with you). 2. will have other form documents through certain format conversion tool (for example the WORD documents) to transform the HTML documents. 3. by the Web server (or said that the HTTP server) one only then real-time dynamic produces. the HTML language is through uses each kind of mark (tags) to mark the documents the structure as well as marks the ultra chain (Hyperlink) the information.Although the HTML language described the documents structure form, but how can't define the documents information to precisely demonstrate and arrange, but is onlysuggested how the Web browser (for example Mosiac, Netscape and so on) should demonstrate and arrange these information, is decided finally in front of user's demonstration result by the Web browser's demonstration style and to the mark explanatory ability. Why is the identical documents the effect which demonstrated in the different browser meets is dissimilar. At present the HTML language's edition is 2.0, it is based on SGML (Standard Generalized Markup Language, standard sets at sign language generally, as soon as is applies mechanically describes digitized documents structure and manages its content complex standard) a subset to evolve comes. Although in next edition's standard HTML3.0 (is also called HTML+) to draw up, but some the partial experimental nature draft standard widely has been used, the mostly outstanding Web browser (for example Netscape and so on) can explain in the HTML3.0 part new mark, therefore introduced in this chapter some HTML3.0 new mark has been accepted by the most browsers.7 Js script language synopsisJS is javascrip, Javascript is one kind the script language which comes by the Netscape LiveScript development, the main purpose is to solve the server terminal language, for instance Perl, carry-over speed question. At that time served the end to need to carry on the confirmation to the data, because the network speed was quite slow, only then 28.8kbps, the confirmation step waste's time were too many. Therefore Netscape browser Navigator has joined Javascript, has provided the data confirmation basic function.The JavaScript official name is “ECMAScript”. This standard by ECMA organization development and maintenance. ECMA-262 is the official JavaScript standard. This standard based on JavaScript (Netscape) and JScript (Microsoft). Netscape (Navigator 2.0) Brendan Eich has invented this language, started from 1996, already appeared in all Netscape and in the Microsoft browser. The ECMA-262 development began in 1996, in 1997 July, the ECMA general meeting has accepted its first edition.Script script uses one specific descriptive language, rests on certain form compilation to be possible the execution document, is also called as great or the batch run document. The script usually may transfer temporarily by the application procedure and carry out. Each kind of script present widely is applied in the homepage design, because the script not only may reduce the homepage the scale and raises the homepage browsing speed,moreover may enrich the homepage performance, like animation, sound and so on. Cites a most common example, when we click in the homepage the E-mail address can transfer Outlook Express or the Foxmail this kind of mail software automatically, is realizes through the script function. Also because of script these characteristics, the human who harbors ulterior motives by some are often using. For example joins some destruction computer system's order in the script, like this works as the user browsing homepage, once transfers this kind of script, will then cause the user the system to come under the attack. Therefore the user should act according to visits homepage the trust degree selective security rank, specially regarding these itself content on the illegal homepage, do not permit the use script easily. Through “the safe establishment” the dialog box, the choice “the script” under option each kind of establishment may with ease realize to script being forbid and begins using.Present's script language is quite many, script language execution generally only with concrete explanation actuator related, so long as therefore on the system has the corresponding language interpreter to be possible to achieve the cross platform. Script (Script), is includes order and so on bind and alias sets, you may save this set are an independent document then in the time which needs carries out, like this may facilitate you in the CS use. The script may save for the suffix named .cfg document places under the cstrike folder, when execution in control bench input: exec (script filename) .cfg then. For instance saves a script is the buys.cfg document, inputs in the control bench: execbuys.cfg may realize the function which we need. Must realize an order, so long as is good this process definition (alias), and assigns a key position for this order, so long as later according to will assign the good key position, may realize this proceJSP及其WEB技术. 1 JSP简介JSP（JavaServer Pages）是一种基于Java的脚本技术。
中英文资料外文翻译An Overview of Servlet and JSP Technology 1.1A Servlet's JobServlets are Java programs that run on Web or application servers, acting as a middle layer between requests coming from Web browsers or other HTTP clients and databases or applications on the HTTP server. Their job is to perform the following tasks, as illustrated in Figure 1-1.Figure 1-11．Read the explicit data sent by the client.The end user normally enters this data in an HTML form on a Web page. However, the data could also come from an applet or a custom HTTP client program.2．Read the implicit HTTP request data sent by the browser.Figure 1-1 shows a single arrow going from the client to the Web server (the layer where servlets and JSP execute), but there are really two varieties of data: the explicit data that the end user enters in a form and the behind-the-scenes HTTP information. Both varieties are critical. The HTTP information includes cookies, information about media types and compression schemes the browser understands, and so on.3．Generate the results.This process may require talking to a database, executing an RMI or EJB call, invoking a Web service, or computing the response directly. Your real data may be in a relational database. Fine. But your database probably doesn't speak HTTP or return results in HTML, so the Web browser can't talk directly to the database. Even if it could, for security reasons, you probably would not want it to. The same argument applies to most other applications. You need the Web middle layer to extract the results inside a document.4．Send the explicit data (i.e., the document) to the client.This document can be sent in a variety of formats, including text (HTML or XML), binary (GIF images), or even a compressed format like gzip that is layered on top of some other underlying format. But, HTML is by far the most common format, so an important servlet/JSP task is to wrap the results inside of HTML.5．Send the implicit HTTP response data.Figure 1-1 shows a single arrow going from the Web middle layer (the servlet or JSP page) to the client. But, there are really two varieties of data sent: the document itself and the behind-the-scenes HTTP information. Again, both varieties are critical to effective development. Sending HTTP response data involves telling the browser or other client what type of document is being returned (e.g., HTML), setting cookies and caching parameters, and other such tasks.1.2Why Build Web Pages Dynamically?Many client requests can be satisfied by prebuilt documents, and the server would handle these requests without invoking servlets. In many cases, however, a static result is not sufficient, and a page needs to be generated for each request. There are a number of reasons why Web pages need to be built on-the-fly:1．The Web page is based on data sent by the client.For instance, the results page from search engines and order-confirmation pages at online stores are specific to particular user requests. You don't know what to display until you read the data that the user submits. Just remember that the user submits twokinds of data: explicit (i.e., HTML form data) and implicit (i.e., HTTP request headers). Either kind of input can be used to build the output page. In particular, it is quite common to build a user-specific page based on a cookie value.2．The Web page is derived from data that changes frequently.If the page changes for every request, then you certainly need to build the response at request time. If it changes only periodically, however, you could do it two ways: you could periodically build a new Web page on the server (independently of client requests), or you could wait and only build the page when the user requests it. The right approach depends on the situation, but sometimes it is more convenient to do the latter: wait for the user request. For example, a weather report or news headlines site might build the pages dynamically, perhaps returning a previously built page if that page is still up to date.3．The Web page uses information from corporate databases or other server-side sources.If the information is in a database, you need server-side processing even if the client is using dynamic Web content such as an applet. Imagine using an applet by itself for a search engine site:"Downloading 50 terabyte applet, please wait!" Obviously, that is silly; you need to talk to the database. Going from the client to the Web tier to the database (a three-tier approach) instead of from an applet directly to a database (a two-tier approach) provides increased flexibility and security with little or no performance penalty. After all, the database call is usually the rate-limiting step, so going through the Web server does not slow things down. In fact, a three-tier approach is often faster because the middle tier can perform caching and connection pooling.In principle, servlets are not restricted to Web or application servers that handle HTTP requests but can be used for other types of servers as well. For example, servlets could be embedded in FTP or mail servers to extend their functionality. And, a servlet API for SIP (Session Initiation Protocol) servers was recently standardized(see /en/jsr/detail?id=116). In practice, however, this use of servlets has not caught on, and we'll only be discussing HTTP servlets.1.3The Advantages of Servlets Over "Traditional" CGIJava servlets are more efficient, easier to use, more powerful, more portable, safer, and cheaper than traditional CGI and many alternative CGI-like technologies.1．EfficientWith traditional CGI, a new process is started for each HTTP request. If the CGI program itself is relatively short, the overhead of starting the process can dominate the execution time. With servlets, the Java virtual machine stays running and handles each request with a lightweight Java thread, not a heavyweight operating system process. Similarly, in traditional CGI, if there are N requests to the same CGI program, the code for the CGI program is loaded into memory N times. With servlets, however, there would be N threads, but only a single copy of the servlet class would be loaded. This approach reduces server memory requirements and saves time by instantiating fewer objects. Finally, when a CGI program finishes handling a request, the program terminates. This approach makes it difficult to cache computations, keep database connections open, and perform other optimizations that rely on persistent data. Servlets, however, remain in memory even after they complete a response, so it is straightforward to store arbitrarily complex data between client requests.2．ConvenientServlets have an extensive infrastructure for automatically parsing and decoding HTML form data, reading and setting HTTP headers, handling cookies, tracking sessions, and many other such high-level utilities. In CGI, you have to do much of this yourself. Besides, if you already know the Java programming language, why learn Perl too? You're already convinced that Java technology makes for more reliable and reusable code than does Visual Basic, VBScript, or C++. Why go back to those languages for server-side programming?3．PowerfulServlets support several capabilities that are difficult or impossible to accomplish with regular CGI. Servlets can talk directly to the Web server, whereas regular CGI programs cannot, at least not without using a server-specific API. Communicating with the Web server makes it easier to translate relative URLs into concrete path names, for instance. Multiple servlets can also share data, making it easy to implement database connection pooling and similar resource-sharing optimizations. Servlets can also maintain information from request to request, simplifying techniques like session tracking and caching of previous computations.4．PortableServlets are written in the Java programming language and follow a standard API. Servlets are supported directly or by a plugin on virtually every major Web server. Consequently, servlets written for, say, Macromedia JRun can run virtually unchanged on Apache Tomcat, Microsoft Internet Information Server (with a separate plugin), IBM WebSphere, iPlanet Enterprise Server, Oracle9i AS, or StarNine WebStar. They are part of the Java 2 Platform, Enterprise Edition (J2EE; see /j2ee/), so industry support for servlets is becoming even more pervasive.5．InexpensiveA number of free or very inexpensive Web servers are good for development use or deployment of low- or medium-volume Web sites. Thus, with servlets and JSP you can start with a free or inexpensive server and migrate to more expensive servers with high-performance capabilities or advanced administration utilities only after your project meets initial success. This is in contrast to many of the other CGI alternatives, which require a significant initial investment for the purchase of a proprietary package.Price and portability are somewhat connected. For example, Marty tries to keep track of the countries of readers that send him questions by email. India was near the top of the list, probably #2 behind the U.S. Marty also taught one of his JSP andservlet training courses (see /) in Manila, and there was great interest in servlet and JSP technology there.Now, why are India and the Philippines both so interested? We surmise that the answer is twofold. First, both countries have large pools of well-educated software developers. Second, both countries have (or had, at that time) highly unfavorable currency exchange rates against the U.S. dollar. So, buying a special-purpose Web server from a U.S. company consumed a large part of early project funds.But, with servlets and JSP, they could start with a free server: Apache Tomcat (either standalone, embedded in the regular Apache Web server, or embedded in Microsoft IIS). Once the project starts to become successful, they could move to a server like Caucho Resin that had higher performance and easier administration but that is not free. But none of their servlets or JSP pages have to be rewritten. If their project becomes even larger, they might want to move to a distributed (clustered) environment. No problem: they could move to Macromedia JRun Professional, which supports distributed applications (Web farms). Again, none of their servlets or JSP pages have to be rewritten. If the project becomes quite large and complex, they might want to use Enterprise JavaBeans (EJB) to encapsulate their business logic. So, they might switch to BEA WebLogic or Oracle9i AS. Again, none of their servlets or JSP pages have to be rewritten. Finally, if their project becomes even bigger, they might move it off of their Linux box and onto an IBM mainframe running IBM WebSphere. But once again, none of their servlets or JSP pages have to be rewritten.6．SecureOne of the main sources of vulnerabilities in traditional CGI stems from the fact that the programs are often executed by general-purpose operating system shells. So, the CGI programmer must be careful to filter out characters such as backquotes and semicolons that are treated specially by the shell. Implementing this precaution is harder than one might think, and weaknesses stemming from this problem are constantly being uncovered in widely used CGI libraries.A second source of problems is the fact that some CGI programs are processed by languages that do not automatically check array or string bounds. For example, in C and C++ it is perfectly legal to allocate a 100-element array and then write into the 999th "element," which is really some random part of program memory. So, programmers who forget to perform this check open up their system to deliberate or accidental buffer overflow attacks.Servlets suffer from neither of these problems. Even if a servlet executes a system call (e.g., with Runtime.exec or JNI) to invoke a program on the local operating system, it does not use a shell to do so. And, of course, array bounds checking and other memory protection features are a central part of the Java programming language.7．MainstreamThere are a lot of good technologies out there. But if vendors don't support them and developers don't know how to use them, what good are they? Servlet and JSP technology is supported by servers from Apache, Oracle, IBM, Sybase, BEA, Macromedia, Caucho, Sun/iPlanet, New Atlanta, ATG, Fujitsu, Lutris, Silverstream, the World Wide Web Consortium (W3C), and many others. Several low-cost plugins add support to Microsoft IIS and Zeus as well. They run on Windows, Unix/Linux, MacOS, VMS, and IBM mainframe operating systems. They are the single most popular application of the Java programming language. They are arguably the most popular choice for developing medium to large Web applications. They are used by the airline industry (most United Airlines and Delta Airlines Web sites), e-commerce (), online banking (First USA Bank, Banco Popular de Puerto Rico), Web search engines/portals (), large financial sites (American Century Investments), and hundreds of other sites that you visit every day.Of course, popularity alone is no proof of good technology. Numerous counter-examples abound. But our point is that you are not experimenting with a new and unproven technology when you work with server-side Java.Servlet和JSP技术简介1.1Servlet的功能Servlets是运行在Web或应用服务器上的Java程序，它是一个中间层，负责连接来自Web浏览器或其他HTTP客户端和HTTP服务器上的数据库或应用程序。
