Servlet 串联过滤器

时间：2023-03-10 04:42:20
Servlet 串联过滤器

1. 串联Servlet过滤器的工作流程

Servlet 串联过滤器

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

Servlet 串联过滤器

打印的顺序与过滤器的工作流程一致

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