简介：

实验多个过滤器进行拦截和放行时的运行顺序：

首先创建AServlet：

package demo1;
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;

@WebServlet("/AServlet")
public class AServlet extends HttpServlet {
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("------Aervlet-----");
    }
}

然后创建两个过滤器：

AFilter：

package demoFilter;
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;

public class AFilter implements Filter {
    /**
     * 创建之后立即执行，用来做初始化，Filter在服务器启动时就创建
     */
    public void init(FilterConfig filterConfig) throws ServletException {
        System.out.println("AFilter：过滤器出生！");
    }
    /**
     * 每次过滤时都会执行
     */
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
            throws IOException, ServletException {
        System.out.println("AFilter：拦截成功！");
        chain.doFilter(request, response);
        System.out.println("AFilter：已放行！");
    }
    /**
     * 销毁之前执行，用来对非内存资源进行释放
     */
    public void destroy() {
        System.out.println("AFilter：过滤器死亡！");
    }

}

BFilter:

package demoFilter;
import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

public class BFilter implements Filter {

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
            throws IOException, ServletException {
        System.out.println("BFilter：拦截成功！");
        chain.doFilter(request, response);    // 放行：让资源请求通过
        System.out.println("BFilter：已放行！");
    }
}

然后在web.xml中配置Filter：

这里AFilter是拦截所有资源，BFilter只拦截AServlet；

<?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_4_0.xsd"
    id="WebApp_ID" version="4.0">
    <display-name>day0412_1</display-name>
    <filter>
        <filter-name>AFilter</filter-name>    <!-- 自定义名称 -->
        <filter-class>demoFilter.AFilter</filter-class> <!-- Filter类所在路径 -->
    </filter>
    <filter-mapping>
        <filter-name>AFilter</filter-name> <!-- 自定义名称匹配 -->
        <url-pattern>/*</url-pattern> <!-- 拦截的资源路径 -->
    </filter-mapping>
    <filter>
        <filter-name>BFilter</filter-name>    <!-- 自定义名称 -->
        <filter-class>demoFilter.BFilter</filter-class> <!-- Filter类所在路径 -->
    </filter>
    <filter-mapping>
        <filter-name>BFilter</filter-name> <!-- 自定义名称匹配 -->
        <url-pattern>/AServlet</url-pattern> <!-- 拦截的资源路径 -->
    </filter-mapping>
</web-app>

再创建一个jsp资源文件：

<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<%@ page language="java" contentType="text/html; charset=utf-8"
    pageEncoding="ISO-8859-1"%>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>my index.jsp</title>
</head>
<body>
<% System.out.println("This is a apple!!!!!"); %>
<h1>This is a JSP named index.jsp!!</h1>
</body>
</html>