java:Filter、Listener 自定义拦截器和过滤器应用

一，Filter

FilterEncoding 过滤器，统一设置servlet的编码格式。

package com.dkt.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;

public class FilterEncoding  implements Filter{
	private String encoding;
	public void destroy() {

	}

	public void doFilter(ServletRequest request, ServletResponse response,
			FilterChain chain) throws IOException, ServletException {
		request.setCharacterEncoding(encoding);
		response.setCharacterEncoding(encoding);
		chain.doFilter(request, response);

	}

	public void init(FilterConfig filterConfig) throws ServletException {
		//   encoding 在web.xml中配置。开启服务器即加载
		 encoding = filterConfig.getInitParameter("encoding");
		 System.out.println(encoding);
	}

}

FilterLogin 过滤器,访问页面时，过滤没有登录的用户，跳转到登录页面

package com.dkt.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;
import javax.servlet.http.HttpSession;

public class FilterLogin  implements Filter{

	public void doFilter(ServletRequest request, ServletResponse response,
			FilterChain chain) throws IOException, ServletException {
		HttpServletRequest hrequest = (HttpServletRequest)request;
		HttpSession session = hrequest.getSession();
		Object name = session.getAttribute("name");
		if (("").equals(name)||name==null) {
			session.setAttribute("error", "*您还没有登录，请先登录");
			/*
			 * 从goodsinfo文件夹下的goodsone页面中，跳转到loginFilter.jsp页面时，需向外跳一级
			 * request.getRequestDispatcher("../loginFilter.jsp").forward(request, response);
			 * 从WEB-INF文件下的userinfo文件夹下的userone.jsp页面跳到loginFilter.jsp页面。
			 * 需要向外跳两级。且WEB-INF文件夹的文件不能再外部通过http直接访问，
			 * 只能通过内部request的方式跳转页面
			 */
			//request.getRequestDispatcher("loginFilter.jsp").forward(request, response);
			request.getRequestDispatcher("loginFilter.jsp").forward(request, response);
		}else {
			chain.doFilter(request, response);
		}
	}

	public void destroy() {

	}

	public void init(FilterConfig arg0) throws ServletException {

	}

}

二，Listener

ListenerOnline 监听器，监听在线人数。并存在application作用域中

package com.dkt.listener;

import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpSessionAttributeListener;
import javax.servlet.http.HttpSessionBindingEvent;
import javax.servlet.http.HttpSessionEvent;
import javax.servlet.http.HttpSessionListener;

public class ListenerOnline implements HttpSessionAttributeListener,
HttpSessionListener{
	private static int count;//统计在线人数

	public void attributeAdded(HttpSessionBindingEvent se) {
		HttpSession session = se.getSession();
		Object username = session.getAttribute("name");
		if (username!=null&&!("").equals(username)) {
			count++;
			session.getServletContext().setAttribute("count", count);
		}

	}

	public void attributeRemoved(HttpSessionBindingEvent se) {

	}

	public void attributeReplaced(HttpSessionBindingEvent se) {

	}

	public void sessionCreated(HttpSessionEvent se) {

	}

	public void sessionDestroyed(HttpSessionEvent se) {
		if (count>0) {
			count--;
			se.getSession().getServletContext().setAttribute("count", count);
		}
	}

}

ListenerR 简单实用监听器

package com.dkt.listener;

import javax.servlet.ServletRequestAttributeEvent;
import javax.servlet.ServletRequestAttributeListener;
import javax.servlet.ServletRequestEvent;
import javax.servlet.ServletRequestListener;

public class ListenerR implements ServletRequestAttributeListener,
ServletRequestListener{

	public void attributeAdded(ServletRequestAttributeEvent srae) {
		System.out.println("属性添加");
	}

	public void attributeRemoved(ServletRequestAttributeEvent srae) {
		System.out.println("属性移除");
	}

	public void attributeReplaced(ServletRequestAttributeEvent srae) {
		System.out.println("属性替换");
	}

	public void requestDestroyed(ServletRequestEvent sre) {
		System.out.println("销毁");
	}

	public void requestInitialized(ServletRequestEvent sre) {
		System.out.println("初始化");
	}

}

三，servlet

TestEncodingTwo 验证FilterEncoding 和 ListenerR 

package com.dkt.servlet;

import java.io.IOException;

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

public class TestEncodingTwo extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		doPost(request, response);
	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		response.setContentType("text/html");
		String name = request.getParameter("name");
		String hobby = request.getParameter("hobby");
        System.out.println(name+"----"+hobby);
        request.setAttribute("name", name);
        request.setAttribute("hobby", hobby);
        /*
			 初始化
			属性替换
			销毁
			初始化
			属性替换
			星星----男
			属性添加
			属性添加
			销毁
         */
	}

}

　　LoginServlet

package com.dkt.servlet;

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

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

import com.dkt.dao.UserJdbc;

public class LoginServlet extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		doPost(request, response);
	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		response.setContentType("text/html");
		request.setCharacterEncoding("utf-8");
		response.setCharacterEncoding("utf-8");
		HttpSession session = request.getSession();
		String op = request.getParameter("op");
		System.out.println("op----------->"+op);
		if (("login").equals(op)) {
			String name = request.getParameter("name");
			String password = request.getParameter("password");
			Boolean bool = new UserJdbc().validate(name, password);
			if (bool) {
				session.setAttribute("name", name);
				request.getRequestDispatcher("/WEB-INF/userinfo/userone.jsp").forward(request, response);
			}else {
				request.getRequestDispatcher("../../loginFilter.jsp").forward(request, response);
			}
		}else if (("a").equals(op)) {
			request.setAttribute("aaa", "apple");
			PrintWriter out = response.getWriter();
			out.print("apple");//responseText;
			out.flush();
			out.close();
		}else if(("exit").equals(op)){
			Object name = session.getAttribute("name");
			session.invalidate();//销毁session
			request.getRequestDispatcher("/WEB-INF/userinfo/userone.jsp").forward(request, response);
		}

	}

}　　

四，jsp

loginFilter.jsp

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">

    <title>My JSP 'MyJsp.jsp' starting page</title>

	<meta http-equiv="pragma" content="no-cache">
	<meta http-equiv="cache-control" content="no-cache">
	<meta http-equiv="expires" content="0">
	<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
	<meta http-equiv="description" content="This is my page">
	<!--
	<link rel="stylesheet" type="text/css" href="styles.css">
	-->

  </head>
  <body>
	<form action="LoginServlet?op=login" method="post">
	   <span style="font-size: 12px;color: red;">${error }</span><br/>
		用户名：<input type="text" name = "name" value=""><br/><br/>
		密  码：<input type="password" name = "password"  ><br/>
		<input type="submit" value="登录">    
	   <input type="reset" value="重置"><br/>
	</form>
    <form action="LoginServlet?op=exit" method="post">
    <input type="submit" value="退出" />
    </form>
  </body>
</html>

　index.jsp

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%@page import="com.dkt.entity.UserInfo"%>
<%@ taglib uri="hello" prefix="hello" %>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">

    <title>My JSP 'index.jsp' starting page</title>
	<meta http-equiv="pragma" content="no-cache">
	<meta http-equiv="cache-control" content="no-cache">
	<meta http-equiv="expires" content="0">
	<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
	<meta http-equiv="description" content="This is my page">
	<!--
	<link rel="stylesheet" type="text/css" href="styles.css">
	-->
  </head>

  <body>
      用户信息：${name }<br/>
    当前在线人数：${count }
    <hr/>

  </body>
</html>

　　

　

五，web.xml

<?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">

	<!-- 配置登录过滤器 -->
	<filter>
			<filter-name>loginfilter</filter-name>
			<filter-class>com.dkt.filter.FilterLogin</filter-class>
	</filter>
	<!-- 过滤器适用于多个页面时，可重复多个filter-mappingm,以提供多个页面进行过滤 -->
	<filter-mapping>
			<filter-name>loginfilter</filter-name>
			<url-pattern>/try.jsp</url-pattern>
	</filter-mapping>
	<filter-mapping>
			<filter-name>loginfilter</filter-name>
			<url-pattern>/goodsinfo/*</url-pattern><!-- 过滤goodsinfo文件夹下的所有文件 -->
	</filter-mapping>
	<filter-mapping>
			<filter-name>loginfilter</filter-name>
			<url-pattern>/WEB-INF/userinfo/*</url-pattern><!-- 过滤WEB-INF文件夹下的userinfo文件夹下的所有文件 -->
	</filter-mapping>
	<filter-mapping>
			<filter-name>loginfilter</filter-name>
			<url-pattern>/FilterServlet</url-pattern><!-- 过滤servlet -->
	</filter-mapping>
	<!-- 当访问temp.jsp页面时会先执行过滤器，如果用户已登录则可访问
	    如果没用登录，session里面没有存name属性，则跳到登录页面，让用户登录.
	    登录成功在跳到temp.jsp
	 -->
	 <!-- 初始化过滤器，统一设置编码格式 -->
	<filter>
			<filter-name>filterEncoding</filter-name>
			<filter-class>com.dkt.filter.FilterEncoding</filter-class>
			<!-- 过滤初始化，设置servlet的编码格式 -->
			<init-param>
					<param-name>encoding</param-name>
					<param-value>utf-8</param-value>
			</init-param>
	</filter>
	<filter-mapping>
			<filter-name>filterEncoding</filter-name>
			<url-pattern>/servlet/*</url-pattern>
<!-- 过滤servlet下的所有servlet，初始化设置编码格式 此servlet下不是包名，是下面的mapping中的url-pattern路径 -->
	</filter-mapping>

	<!-- request监听 -->
	<listener>
		<listener-class>com.dkt.listener.ListenerR</listener-class>
	</listener>
	<listener>
		<listener-class>com.dkt.listener.ListenerOnline</listener-class>
	</listener>

  <servlet>
    <servlet-name>LoginServlet</servlet-name>
    <servlet-class>com.dkt.servlet.LoginServlet</servlet-class>
  </servlet>
  <servlet>
    <servlet-name>TestEncodingTwo</servlet-name>
    <servlet-class>com.dkt.servlet.TestEncodingTwo</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>LoginServlet</servlet-name>
    <url-pattern>/LoginServlet</url-pattern>
  </servlet-mapping>
  <servlet-mapping>
    <servlet-name>TestEncodingTwo</servlet-name>
    <url-pattern>/servlet/TestEncodingTwo</url-pattern>
  </servlet-mapping>

  <welcome-file-list>
  	<welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
</web-app>