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Servlet 串联过滤器

Posted on 2017-10-22 10:54  work hard work smart  阅读(383)  评论(0)  编辑  收藏  举报

 

1. 串联Servlet过滤器的工作流程

 

2. 创建两个过滤器 MyFilter1和MyFilter2

1） MyFilter1

package com.example.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.annotation.WebFilter;

/**
 * Servlet Filter implementation class MyFilter1
 */
//@WebFilter("/MyFilter1")
public class MyFilter1 implements Filter {

    /**
     * Default constructor. 
     */
    public MyFilter1() {
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see Filter#destroy()
	 */
	public void destroy() {
		// TODO Auto-generated method stub
	}

	/**
	 * @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
		System.out.println("dofilter 1");
		// pass the request along the filter chain
		chain.doFilter(request, response);
		System.out.println("after dofilter 1");
	}

	/**
	 * @see Filter#init(FilterConfig)
	 */
	public void init(FilterConfig fConfig) throws ServletException {
		// TODO Auto-generated method stub
	}

}

　　2） MyFilter 2

package com.example.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.annotation.WebFilter;

/**
 * Servlet Filter implementation class MyFilter2
 */
//@WebFilter("/MyFilter2")
public class MyFilter2 implements Filter {

    /**
     * Default constructor. 
     */
    public MyFilter2() {
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see Filter#destroy()
	 */
	public void destroy() {
		// TODO Auto-generated method stub
	}

	/**
	 * @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
		System.out.println("dofilter 2");
		// pass the request along the filter chain
		chain.doFilter(request, response);
		System.out.println("after dofilter 2");
	}

	/**
	 * @see Filter#init(FilterConfig)
	 */
	public void init(FilterConfig fConfig) throws ServletException {
		// TODO Auto-generated method stub
	}

}

　　

3) 在web.xml 中配置过滤器

 <filter>
    <filter-name>MyFilter1</filter-name>
    <filter-class>com.example.filter.MyFilter1</filter-class>
  </filter>
  <filter-mapping>
    <filter-name>MyFilter1</filter-name>
    <url-pattern>/InfoServlet</url-pattern>
  </filter-mapping>
  
  <filter>
    <filter-name>MyFilter2</filter-name>
    <filter-class>com.example.filter.MyFilter2</filter-class>
  </filter>
  <filter-mapping>
    <filter-name>MyFilter2</filter-name>
    <url-pattern>/InfoServlet</url-pattern>
  </filter-mapping>

　　

4） 创建jsp页面

<%@ 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="InfoServlet">
	username: <input type="text" name="username"><br>
	<input type="submit" value="submit">
</form>
</body>
</html>

　　

5） 创建InfoServlet

package com.example.servlet;

import java.io.IOException;
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 InfoServlet
 */
@WebServlet("/InfoServlet")
public class InfoServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public InfoServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		System.out.println(request.getParameter("username"));
		request.getRequestDispatcher("infoResult.jsp").forward(request, response);
	}

}

　　

6） 显示结果

 

 打印的顺序与过滤器的工作流程一致