过滤器简单应用

用过滤器处理字符编码问题（java内部采用Unicoder，处理中文会乱码）

index.jsp:

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>

</head>
<body>
<form action="/FilterTest/MyServlet" method="post">
<p>请输入你的中文名字：</p>
<input type="text" name="username">
<input type="submit" value="提交">
</form>
</body>
</html>

View Code

MyFilter过滤器:

package com.zjlyyq;

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.annotation.WebFilter;

/**
 * Servlet Filter implementation class MyFilter
 */
@WebFilter("/MyFilter")
public class MyFilter implements Filter {
    //FilterConfig filterConfig = null;
    String encoding = null;
    /**
     * Default constructor. 
     */
    public MyFilter() {
        // TODO Auto-generated constructor stub
    }

    /**
     * @see Filter#destroy()
     */
    public void destroy() {
        // TODO Auto-generated method stub
        //this.filterConfig = null;
        this.encoding = null;
    }

    /**
     * @see Filter#doFilter(ServletRequest, ServletResponse, FilterChain)
     */
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        // TODO Auto-generated method stub
        // place your code here
        if(encoding != null){
            System.out.println("2");
            request.setCharacterEncoding(encoding);
            response.setContentType("text/html;charset="+encoding);
        }
        // pass the request along the filter chain
        chain.doFilter(request, response);
    }

    /**
     * @see Filter#init(FilterConfig)
     */
    public void init(FilterConfig fConfig) throws ServletException {
        // TODO Auto-generated method stub
        System.out.println("1");
        //this.filterConfig = fConfig;
        this.encoding = fConfig.getInitParameter("encoding");
        System.out.println(this.encoding);
    }

}

View Code

MyServlet:

package com.zjlyyq;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class MyServlet
 */
@WebServlet("/MyServlet")
public class MyServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public MyServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        //response.getWriter().append("Served at: ").append(request.getContextPath());
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        //doGet(request, response);
        PrintWriter out = response.getWriter();
        String name = request.getParameter("username");
        out.print("你好，"+ name+"<br>");
        out.print("<a href=index.jsp>返回</a>");
    }
}

View Code

web.xml:

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
  <display-name>FilterTest</display-name>
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>
  <filter>
    <filter-name>MyFilter</filter-name>
    <filter-class>com.zjlyyq.MyFilter</filter-class>
    <init-param>
      <param-name>encoding</param-name>
      <param-value>UTF-8</param-value>
    </init-param>
  </filter>
  <filter-mapping>
    <filter-name>MyFilter</filter-name>
    <url-pattern>/*</url-pattern>
    <dispatcher>REQUEST</dispatcher>
    <dispatcher>FORWARD</dispatcher>
  </filter-mapping>
  <servlet>
      <servlet-name>SimpleServlet</servlet-name>
      <servlet-class>com.zjlyyq.MyServlet</servlet-class>
  </servlet>
  <servlet-mapping>
      <servlet-name>SimpleServlet</servlet-name>
      <url-pattern>/FilterTest/MyServlet</url-pattern>
  </servlet-mapping>
</web-app>

View Code

运行结果：