5.Servlet过滤器的使用

1.什么是Servlet过滤器？

     我们日常生活中的水物质 过滤器是采用不同滤料对水进行过滤，到达去除水中部分杂质的一种设备。而web服务中的Servlet过滤器的功能和水物质过滤器的功能类似。servlet过滤器的作用就是根据过滤 条件对HTTP请求进行过滤.

2.Servlet过滤器的功能

• 网站内容访问权限过滤
• 网站信息发布、修改，屏蔽非法字符
• 对请求内容进行 统一编码

3.编码

package com.tao.common.power.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.http.HttpServletRequest;

public class PowerFilter implements Filter {

	public void init(FilterConfig filterConfig) throws ServletException {
		
	}

	public void doFilter(ServletRequest request, ServletResponse response,
			FilterChain chain) throws IOException, ServletException {
		boolean flag = true;
		HttpServletRequest req = (HttpServletRequest) request;
		System.out.println(req.getRequestURI());
		if (flag) {
			chain.doFilter(request, response);
		} else {
			request.getRequestDispatcher("/error/power.jsp").forward(request, response);
		}
	}

	public void destroy() {

	}

}

 4.配置

<?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">

	<!-- 权限控制  -->
	<filter>
		<filter-name>power</filter-name>
		<filter-class>com.tao.common.power.filter.PowerFilter</filter-class>
	</filter>
	<filter-mapping>
		<filter-name>power</filter-name>
		<url-pattern>/*</url-pattern>
	</filter-mapping>
</web-app>