Servlet中url-pattern詳解

過濾器概述

       過濾器就好比應用中的保安，利用過濾器實現對請求和響應的攔截。

編寫過濾器的步驟

編寫一個類，實現javax.servlet.Filter接口

package com.bjpowernode.servlet;

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 FilterDemo1 implements Filter {


    //由容器調用：完成過濾器的初始化
    public void init(FilterConfig filterConfig) throws ServletException {
        // TODO Auto-generated method stub

    }


    //由容器調用，每次請求和響應都會經過該方法
    public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain chain) throws IOException, ServletException {
        System.out.println("FilterDemo1過濾器執行了");
        chain.doFilter(request, response);  //放行，讓下一個資源執行

    }
    //由容器調用：完成過濾器銷燬時的清理工作
    public void destroy() {
        // TODO Auto-generated method stub

    }
}

配置文件 web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5"
    xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
    http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
  <display-name></display-name>
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
 <filter>
    <filter-name>FilterDemo1</filter-name>
    <filter-class>com.bjpowernode.servlet.FilterDemo1</filter-class>
 </filter>
 <filter-mapping>
    <filter-name>FilterDemo1</filter-name>
    <url-pattern>/*</url-pattern>
 </filter-mapping>
</web-app>