Servlet过滤器使用

<?xml version="1.0" encoding="UTF-8"?>
<web-app id="WebApp_ID" version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
	<display-name>TestFilter</display-name>
	<welcome-file-list>
		<welcome-file>index.html</welcome-file>
		<welcome-file>index.htm</welcome-file>
		<welcome-file>index.jsp</welcome-file>
		<welcome-file>default.html</welcome-file>
		<welcome-file>default.htm</welcome-file>
		<welcome-file>default.jsp</welcome-file>
	</welcome-file-list>
	<filter>
		<filter-name>SysFilter</filter-name>
		<filter-class>com.lwf.servlet.SysFilter</filter-class>
	</filter>
	<filter-mapping>
		<filter-name>SysFilter</filter-name>
		<url-pattern>/LoginServlet</url-pattern>
	</filter-mapping>
	<servlet>
		<servlet-name>LoginServlet</servlet-name>
		<servlet-class>com.lwf.servlet.LoginServlet</servlet-class>
	</servlet>
	<servlet-mapping>
		<servlet-name>LoginServlet</servlet-name>
		<url-pattern>/LoginServlet</url-pattern>
	</servlet-mapping>
</web-app>

 

过滤器类：

package com.lwf.servlet;

import java.io.IOException;
import java.io.PrintWriter;

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.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;

public class SysFilter extends HttpServlet implements Filter {

	private FilterConfig config;
	public void doFilter(ServletRequest req, ServletResponse resp,
			FilterChain filterChain) throws IOException, ServletException {
		HttpServletRequest request = (HttpServletRequest)req;
		String name = request.getParameter("name");
		String pwd = request.getParameter("pwd");
		if(name.equals("lwf") && pwd.equals("lwf")){
			filterChain.doFilter(req, resp);
		}else{
			PrintWriter out = resp.getWriter();
			String script = "<script language=\"javascript\">alert('sf');" +
					"window.location.href='./index.jsp'" +
					"</script>";
			out.print(script);
		}
	}

	public void init(FilterConfig arg0) throws ServletException {
		this.config = arg0;
	}

}

 附件为代码示例。

本文只提供一个简单的示例。