javaweb实现简单留⾔板功能本⽂实例为⼤家分享了java web实现简单留⾔板的具体代码，供⼤家参考，具体内容如下⼀、⽬标⽤户可以登录并记住密码进⼊留⾔板，添加留⾔，点击留⾔列表中的标题可显⽰该条留⾔全部内容。
⼆、相关知识1、使⽤Cookie实现⾃动登录⽤户第⼀次登录⽹站，服务器将⽤户名和密码以Cookie的形式发送到客户端。
当客户之后再次访问该⽹站时，浏览器⾃动将Cookie⽂件中的⽤户名和密码随请求⼀起发送到服务器，服务器从Cookie中取出⽤户名和密码并且通过验证。
2、java类的定义与使⽤定义java类时注意属性的定义、构造⽅法的重写，定义两个⽅法，⼀个是访问⽅法（getter），⼀个是修改⽅法（setter）。
三、实现思路1、登录输⼊⽤户名、密码登录，对应检测登录BoardLoginServlet可实现记住登录信息 Cookie实现登录成功显⽰留⾔板标题列表页⾯board-title.jsp，登录失败返回登录页⾯2、显⽰留⾔标题标题列表为上下⽂变量lists，其中标题为链接，点击可显⽰留⾔具体信息界⾯（跳转到MessageServlet处理）。
list = username+":"+"<a href='MessageServlet?title="+title+"'target='_parent'>"+title+"</a>";页⾯下⽅有新增留⾔的链接，点击后跳转到写留⾔页⾯<a href="board-write.jsp" rel="external nofollow" rel="external nofollow" >新增留⾔</a>3、添加留⾔输⼊标题、内容 post给WriteServlet4、显⽰留⾔具体信息在MessageServlet中遍历查找留⾔并传递变量，显⽰留⾔信息在board-message.jsp四、代码实现board-login.jsp<form action="board.do" method="post"><br><h1 class="text" >登录界⾯</h1>昵称：<input type="text" name="username" value="${ername.value}"/><br>密码：<input type="password" name="password" value="${cookie.password.value}"/><br><br><input type="checkbox" name="check" value="check"/>记住密码<br> <br><input type="submit" value="登录"/><input type="reset" value="取消"/></form>board-title.jsp<h2>留⾔板</h2>${lists}<a href="board-write.jsp" rel="external nofollow" rel="external nofollow" >新增留⾔</a>boarrd-write.jsp<form action="write.do" method="post">标题:<input type="text" name="title"/><br>内容:<input type="text" name="text"/><br><input type="submit"/></form>board-message.jsp<h2>留⾔详情</h2>⽤户名：${name}<br>标题：${title}<br>内容：${text}<br>时间：${date}<br>Message.java（将留⾔信息存储在Message类中）package board;import java.util.Date;public class Message {private String title;//标题private String time;//时间private String username;//⽤户名private String text;//内容public Message(){}//初始化public Message(String title,String time,String username,String text){this.title = title;this.time = time;ername = username;this.text = text;}public String getTitle(){return title;}public String getUsername(){return username;}public String getTime(){return time;}public String getText(){return text;}}BoardLoginServlet.java（⽤Cookie登录）package board;import javax.servlet.ServletException;import javax.servlet.http.*;import java.io.IOException;@javax.servlet.annotation.WebServlet(name = "BoardLoginServlet",urlPatterns = "/board.do")public class BoardLoginServlet extends HttpServlet {protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { }protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset = utf-8");request.setCharacterEncoding("UTF-8");HttpSession session=request.getSession();String username = request.getParameter("username").trim();String password = request.getParameter("password").trim();session.setAttribute("username",username);if (!(username.equals("admin") &&password.equals("admin"))&&!(username.equals("123") &&password.equals("123"))) {response.sendRedirect("board-login.jsp");} else {if ((request.getParameter("check") != null) && (request.getParameter("check").equals("check"))) {Cookie nameCookie = new Cookie("username", username);Cookie pswdCookie = new Cookie("password", password);nameCookie.setMaxAge(60 * 60);pswdCookie.setMaxAge(60 * 60);nameCookie.setPath("/");pswdCookie.setPath("/");response.addCookie(nameCookie);response.addCookie(pswdCookie);String value1 = "", value2 = "";Cookie cookie = null;Cookie[] cookies = request.getCookies();if (cookies != null) {for (int i = 0; i < cookies.length; i++) {cookie = cookies[i];if (cookie.getName().equals("username"))value1 = cookie.getValue();if (cookie.getName().equals("password"))value2 = cookie.getValue();}if (value1.equals("admin") && value2.equals("admin")||value1.equals("123") && value2.equals("123")) {response.sendRedirect("board-title.jsp");} else {response.sendRedirect("board-login.jsp");}}}else{response.sendRedirect("board-title.jsp");}}}}WriteServlet.java（新增留⾔）package board;import javax.servlet.RequestDispatcher;import javax.servlet.ServletContext;import javax.servlet.ServletException;import javax.servlet.annotation.WebServlet;import javax.servlet.http.*;import java.io.IOException;import java.text.SimpleDateFormat;import java.util.ArrayList;import java.util.Date;import java.util.List;@WebServlet(name = "WriteServlet",urlPatterns = "/write.do")public class WriteServlet extends HttpServlet {//messages列表中存放Message类对象public List<Message> messages = new ArrayList<Message>();protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=utf-8");ServletContext context = request.getServletContext();HttpSession session = request.getSession();//⽤户名存储到session中String username =(String)session.getAttribute("username");String title = request.getParameter("title");String text = request.getParameter("text");//获取当前时间SimpleDateFormat formatter= new SimpleDateFormat("yyyy-MM-dd 'at' HH:mm:ss");Date date = new Date(System.currentTimeMillis());String time = formatter.format(date);//在messages列表中添加留⾔对象messages.add(new Message(title,time,username,text));context.setAttribute("messages",messages);String list = new String();//list中存放留⾔⽤户名+留⾔标题，标题为链接，可跳转到留⾔具体信息，并传参titlelist = username+":"+"<a href='MessageServlet?title="+title+"'target='_parent'>"+title+"</a>";String lists = new String();//将留⾔标题列表信息存到上下⽂对象if(context.getAttribute("lists")!=null){lists = context.getAttribute("lists") + list + "<br>";}else{lists = list + "<br>";}context.setAttribute("lists", lists);request.setAttribute("lists", lists);//转发RequestDispatcher dispatcher = request.getRequestDispatcher("/board-title.jsp");dispatcher.forward(request, response);}protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { }}MessageServlet.javapackage board;import .httpserver.HttpContext;import javax.servlet.RequestDispatcher;import javax.servlet.ServletContext;import javax.servlet.ServletException;import javax.servlet.annotation.WebServlet;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import java.io.IOException;import java.io.PrintWriter;import java.util.ArrayList;import java.util.List;@WebServlet(name = "MessageServlet",urlPatterns = "/MessageServlet")public class MessageServlet extends HttpServlet {protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { }protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=utf-8");ServletContext context = request.getServletContext();List<Message> messages = new ArrayList<Message>();//获取列表messages = (List<Message>)context.getAttribute("messages");//获取链接中的参数titleString title =request.getParameter("title");String name = new String();String date = new String();String text = new String();//遍历列表，查找该title的具体信息for(Message message : messages){if((message.getTitle()).equals(title)){name = message.getUsername();date = message.getTime();text = message.getText();title = message.getTitle();request.setAttribute("name",name);request.setAttribute("title",title);request.setAttribute("text",text);request.setAttribute("date",date);break;}}//将留⾔信息转发到board-message.jspRequestDispatcher dispatcher = request.getRequestDispatcher("/board-message.jsp");dispatcher.forward(request, response);}}（以上仅为部分代码）以上就是本⽂的全部内容，希望对⼤家的学习有所帮助，也希望⼤家多多⽀持。
