JavaWeb过滤器详解
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JavaWeb过滤器详解
过滤器是什么玩意？
所谓过滤器，其实就是⼀个服务端组件，⽤来截取⽤户端的请求与响应信息。
过滤器的应⽤场景：
1.对⽤户请求进⾏统⼀认证，保证不会出现⽤户账户安全性问题
2.编码转换，可在服务端的过滤器中设置统⼀的编码格式，避免出现乱码
3.对⽤户发送的数据进⾏过滤替换
4.转换图像格式
5.对响应的内容进⾏压缩
其中，第1,2场景经常涉及。
login.jsp
<%@ page language="java" import="java.util.*" contentType="text/html; charset=utf-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
My JSP 'login.jsp' starting page
⽤户名:
密码:
success.jsp
<%@ page language="java" import="java.util.*" pageEncoding="utf-8" contentType="text/html; charset=utf-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
My JSP 'index.jsp' starting page
failure.jsp
<%@ page language="java" import="java.util.*" contentType="text/html; charset=utf-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>
My JSP 'login.jsp' starting page
登录失败，请检查⽤户名或密码！
LoginFilter.java
package com.cityhuntshou.filter;
import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
public class LoginFilter implements Filter {
private FilterConfig config;
public void destroy() {
}
public void doFilter(ServletRequest arg0, ServletResponse arg1,
FilterChain arg2) throws IOException, ServletException {
HttpServletRequest request = (HttpServletRequest) arg0;
HttpServletResponse response = (HttpServletResponse) arg1;
HttpSession session = request.getSession();
//过滤器实际应⽤场景之⼆-----编码转换
String charset = config.getInitParameter("charset");
if(charset == null)
{
charset = "UTF-8";
}
request.setCharacterEncoding(charset);
String noLoginPaths = config.getInitParameter("noLoginPaths");
if(noLoginPaths != null)
{
String[] strArray = noLoginPaths.split(";");
for(int i = 0; i < strArray.length; i++)
{
//空元素，放⾏
if(strArray[i] == null || "".equals(strArray[i]))
continue;
if(request.getRequestURI().indexOf(strArray[i]) != -1)
{
arg2.doFilter(arg0, arg1);
return;
}
}
}
if(request.getRequestURI().indexOf("login.jsp") != -1
|| request.getRequestURI().indexOf("LoginServlet") != -1)
{
arg2.doFilter(arg0, arg1);
return;
}
if(session.getAttribute("username") != null)
{
arg2.doFilter(arg0, arg1);
}
else
{
response.sendRedirect("login.jsp");
}
}
public void init(FilterConfig arg0) throws ServletException {
config = arg0;
}
}
LoginServlet.java
package com.cityhuntshou.servlet;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
public class LoginServlet extends HttpServlet {
/**
* Constructor of the object.
*/
public LoginServlet() {
super();
}
/**
* Destruction of the servlet.
*/
public void destroy() {
super.destroy(); // Just puts "destroy" string in log
// Put your code here
}
/**
* The doGet method of the servlet.
*
* This method is called when a form has its tag value method equals to get.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
