JavaWeb-Filter過濾器

 filter文件

package com.filter;

import javax.servlet.*;

import java.io.IOException;

public class FilterDemo implements Filter {
	// init初始化過濾器
	public void init(FilterConfig config) throws ServletException {
		System.out.println("---過濾器初始化---");
		// 輸出Filter的Name
		System.out.println("過濾器名稱:" + config.getFilterName());
	}

	// 此方法實現過濾操作
	public void doFilter(ServletRequest req, ServletResponse resp,
			FilterChain chain) throws ServletException, IOException {
		// 對request和response進行一些預處理
		System.out.println("執行前:");
		chain.doFilter(req, resp);// 讓目標資源執行,放行
		System.out.println("執行後:");

	}

	// 銷燬過濾器
	public void destroy() {
		System.out.println("---過濾器銷燬---");
	}

}

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">
  <display-name>WebWeb</display-name>

  <filter>
    <filter-name>MyFilter</filter-name>
    <filter-class>com.filter.FilterDemo</filter-class>
  </filter>
  <filter-mapping>
    <filter-name>MyFilter</filter-name>
    <url-pattern>/*</url-pattern>
  </filter-mapping>
</web-app>