过滤器

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 {

//由容器调用：完成过滤器的初始化
public void init(FilterConfig filterConfig) throws ServletException {
// TODO Auto-generated method stub

}

//由容器调用，每次请求和响应都会经过该方法
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
System.out.println("FilterDemo1过滤器执行了");
chain.doFilter(request, response);	//放行，让下一个资源执行

}
//由容器调用：完成过滤器销毁时的清理工作
public void destroy() {
// TODO Auto-generated method stub

}
}

<?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>