[1] JSP里的一个最简单的过滤器(filter)的例子

更新时间：2021-07-11 22:30:04

<%@ page import="java.io.*,java.util.*" %>
<html>
<head>
<title>Auto Refresh Header Example</title>
</head>
<body>
<center>
<h2>Auto Refresh Header Example</h2>
<%    response.setIntHeader("Refresh", 5);    
      Calendar calendar = new GregorianCalendar();    
      String am_pm;    
      int hour = calendar.get(Calendar.HOUR);    
      int minute = calendar.get(Calendar.MINUTE);    
      int second = calendar.get(Calendar.SECOND);    
      if(calendar.get(Calendar.AM_PM) == 0)       
         am_pm = "AM";    
      else       
         am_pm = "PM";    
      String CT = hour+":"+ minute +":"+ second +" "+ am_pm;    
      out.println("Current Time is: " + CT + "\n"); 
%>
</center>
</body>
</html>

在开发包com.sap.jerry中创建新的filter：

package com.sap.jerry;

import javax.servlet.*;
import java.util.*;

public class LogFilter implements Filter  {
       public void  init(FilterConfig config) 
                             throws ServletException{
          // 获取初始化参数
          String testParam = config.getInitParameter("test-param"); 
     
          //打印初始化参数
          System.out.println("Test Param: " + testParam); 
       }
       public void  doFilter(ServletRequest request, 
                     ServletResponse response,
                     FilterChain chain) 
                     throws java.io.IOException, ServletException {
     
          // 获取客户端ip地址  
          String ipAddress = request.getRemoteAddr();
     
          // 输出ip地址及当前时间
          System.out.println("IP "+ ipAddress + ", Time "
                                           + new Date().toString());
     
          // 传递请求道过滤器链
          chain.doFilter(request,response);
       }
       public void destroy( ){
          /* 在Filter实例在服务器上被移除前调用。*/
       }
    }

在WebContent/WEB-INF文件夹下的web.xml里，添加filter的声明：

[1] JSP里的一个最简单的过滤器(filter)的例子

<?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>jerryjsp</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>LogFilter</filter-name>
   <filter-class>com.sap.jerry.LogFilter</filter-class>
   <init-param>
      <param-name>test-param</param-name>
      <param-value>Initialization Paramter</param-value>
   </init-param>
</filter>
<filter-mapping>
   <filter-name>LogFilter</filter-name>
   <url-pattern>/*</url-pattern>
</filter-mapping>
</web-app>

之后即可在console页面里观察到filter类打印的输出：

[1] JSP里的一个最简单的过滤器(filter)的例子

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[1] JSP里的一个最简单的过滤器(filter)的例子

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