本文實(shí)例講述了Java中的攔截器、過(guò)濾器、監(jiān)聽(tīng)器用法。分享給大家供大家參考，具體如下：
一、攔截器 ：是在面向切面編程的就是在你的service或者一個(gè)方法，前調(diào)用一個(gè)方法，或者在方法后調(diào)用一個(gè)方法比如動(dòng)態(tài)代理就是攔截器的簡(jiǎn)單實(shí)現(xiàn)，在你調(diào)用方 法前打印出字符串（或者做其它業(yè)務(wù)邏輯的操作），也可以在你調(diào)用方法后打印出字符串，甚至在你拋出異常的時(shí)候做業(yè)務(wù)邏輯的操作。
1.Struts2攔截器是在訪問(wèn)某個(gè)Action或Action的某個(gè)方法，字段之前或之后實(shí)施攔截，并且Struts2攔截器是可插拔的，攔截器是ＡＯＰ的一種實(shí)現(xiàn)。
2.攔截器棧（Interceptor Stack）Struts2攔截器棧就是將攔截器按一定的順序聯(lián)結(jié)成一條鏈。在訪問(wèn)被攔截的方法或字段時(shí)，Struts2攔截器鏈中的攔截器就會(huì)按其之前定義的順序被調(diào)用。
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package com.lzw.struts.Interceptor;import com.opensymphony.xwork2.ActionInvocation;import com.opensymphony.xwork2.interceptor.MethodFilterInterceptor;public class MyInterceptor extends MethodFilterInterceptor { private static final long serialVersionUID = -6410044851077844880L; /** * 在struts.xml <param name="lzw">struts</param> */ private String lzw; public String getLzw() { return lzw; } public void setLzw(String lzw) { this.lzw = lzw; } @Override public void destroy() { System.out.println("destroy!"); } @Override public void init() { System.out.println("init!"); } @Override protected String doIntercept(ActionInvocation invocation) throws Exception { System.out.println("MyInterceptor-start"); System.out.println(lzw); String result = invocation.invoke(); System.out.println("MyInterceptor-end"); return result; }} |
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package com.lzw.struts.Interceptor;import com.opensymphony.xwork2.ActionInvocation;import com.opensymphony.xwork2.interceptor.MethodFilterInterceptor;public class FirstInterceptor extends MethodFilterInterceptor { private static final long serialVersionUID = 1L; @Override protected String doIntercept(ActionInvocation invocation) throws Exception { System.out.println("FirstInterceptor-Start"); String result = invocation.invoke(); System.out.println("FirstInterceptor-End"); return result; }} |
struts.xml
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<?xml version="1.0" encoding="UTF-8" ?><!DOCTYPE struts PUBLIC "-//Apache Software Foundation//DTD Struts Configuration 2.3//EN" "http://struts.apache.org/dtds/struts-2.3.dtd"><struts> <!--開(kāi)發(fā)模式開(kāi)關(guān)，本地可以設(shè)為true幫助調(diào)試問(wèn)題，部署到服務(wù)器上設(shè)為false--> <constant name="struts.devMode" value="false"/> <!--務(wù)必配上該屬性，否則會(huì)導(dǎo)致AOP注入異常--> <constant name="struts.objectFactory.spring.autoWire.alwaysRespect" value="true"/> <constant name="struts.i18n.encoding" value="UTF-8" /> <constant name="struts.multipart.maxSize" value="1000000000"/> <package name="strutsLzw" extends="struts-default" namespace="/"> <interceptors> <interceptor name="lzwInterceptorA" class="com.lzw.struts.Interceptor.MyInterceptor"> <param name="lzw">struts</param> </interceptor> <interceptor name="lzwInterceptorB" class="com.lzw.struts.Interceptor.FirstInterceptor"> </interceptor> <!-- 定義自己的攔截器棧 --> <interceptor-stack name="myStack"> <interceptor-ref name="lzwInterceptorA"></interceptor-ref> <interceptor-ref name="lzwInterceptorB"></interceptor-ref> <interceptor-ref name="defaultStack"></interceptor-ref> </interceptor-stack> </interceptors> <!-- 全局的每個(gè)action都會(huì)攔截 --> <default-interceptor-ref name="myStack"></default-interceptor-ref> <!-- 增加method="lzwTest" 執(zhí)行LoginAction的lzwTest方法 否則執(zhí)行execute方法 --> <action name="login" class="com.lzw.struts.action.LoginAction" method="lzwTest"> <result name="success">/result.jsp</result> <result name="failer">/error.jsp</result> <result name="input">/error.jsp</result> </action> </package></struts> |
或者：
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<?xml version="1.0" encoding="UTF-8" ?><!DOCTYPE struts PUBLIC "-//Apache Software Foundation//DTD Struts Configuration 2.3//EN" "http://struts.apache.org/dtds/struts-2.3.dtd"><struts> <package name="strutsLzw" extends="struts-default"> <interceptors> <interceptor name="lzwInterceptor" class="com.lzw.struts.Interceptor.MyInterceptor"> <param name="lzw">struts</param> </interceptor> </interceptors> <!-- 增加method="lzwTest" 執(zhí)行LoginAction的lzwTest方法 否則執(zhí)行execute方法 --> <action name="login" class="com.lzw.struts.action.LoginAction" method="lzwTest"> <result name="success">/result.jsp</result> <result name="failer">/error.jsp</result> <result name="input">/error.jsp</result> <interceptor-ref name="lzwInterceptor"></interceptor-ref> <!--增加defaultStack 否則 驗(yàn)證攔截器不執(zhí)行，也就是 validate 方法不執(zhí)行--> <interceptor-ref name="defaultStack"></interceptor-ref> </action> </package></struts> |
web.xml中加入：
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<filter> <filter-name>struts2</filter-name> <!-- 已經(jīng)過(guò)時(shí)了<filter-class>org.apache.struts2.dispatcher.FilterDispatcher</filter-class> --> <filter-class>org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter</filter-class> <init-param> <param-name>actionPackages</param-name> <param-value>com.lzw.struts.action</param-value> </init-param> </filter> <filter-mapping> <filter-name>struts2</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> |
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package com.lzw.struts.action;import com.opensymphony.xwork2.ActionSupport;public class LoginAction extends ActionSupport{ private static final long serialVersionUID = 1L; private String username; private String password; public String getUsername() { return username; } public void setUsername(String username) { this.username = username; } public String getPassword() { return password; } public void setPassword(String password) { this.password = password; } @Override public String execute() throws Exception { System.out.println("=====execute====="); if ("hello".equals(this.getUsername().trim()) && "world".equals(this.getPassword().trim())) { return "success"; } else { this.addFieldError("username", "username or password error"); return "failer"; } } @Override public void validate() { System.out.println("=====validate====="); if (null == this.getUsername() || "".equals(this.getUsername().trim())) { this.addFieldError("username", "username required"); } if (null == this.getPassword() || "".equals(this.getPassword().trim())) { this.addFieldError("password", "password required"); } } public String lzwTest() { System.out.println("======Test===="); return SUCCESS; }} |
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<%@ page language="java" import="java.util.*" pageEncoding="ISO-8859-1"%><%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%>" rel="external nofollow" > <title>My JSP 'login.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" rel="external nofollow" > --> </head> <body> <form action="login.action" method="post"> username:<input type="text" name="username"><br> password:<input type="password" name="password"><br> <input type="submit" value="submit"> </form> </body></html> |
控制臺(tái)結(jié)果：
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init!2013-10-31 13:51:15 org.apache.coyote.AbstractProtocol start信息: Starting ProtocolHandler ["http-apr-8080"]2013-10-31 13:51:15 org.apache.coyote.AbstractProtocol start信息: Starting ProtocolHandler ["ajp-apr-8009"]2013-10-31 13:51:15 org.apache.catalina.startup.Catalina start信息: Server startup in 1699 msMyInterceptor-startstrutsFirstInterceptor-Start=====validate===========Test====FirstInterceptor-EndMyInterceptor-end |
二、過(guò)濾器：是在java web中，你傳入的request,response提前過(guò)濾掉一些信息，或者提前設(shè)置一些參數(shù)，然后再傳入servlet或者struts的 action進(jìn)行業(yè)務(wù)邏輯，比如過(guò)濾掉非法url（不是login.do的地址請(qǐng)求，如果用戶沒(méi)有登陸都過(guò)濾掉）,或者在傳入servlet或者struts的action前統(tǒng)一設(shè)置字符集，或者去除掉一些非法字符。主要為了減輕服務(wù)器負(fù)載，減少壓力
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package com.lzw.filter.demo;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.HttpServletResponse;import javax.servlet.http.HttpSession;public class UserAccessFilter implements Filter{ @Override public void destroy() { System.out.println("destroy!"); } @Override public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException { HttpServletRequest request = (HttpServletRequest)req; HttpServletResponse response = (HttpServletResponse)res; HttpSession session = request.getSession(); if(session.getAttribute("user")== null && request.getRequestURI().indexOf("login.jsp")==-1 ){ response.sendRedirect("login.jsp"); return ; } chain.doFilter(req, res); } @Override public void init(FilterConfig config) throws ServletException { //ApplicationFilterConfig[name=UserFilter, filterClass=com.lzw.filter.demo.UserAccessFilter] System.out.println(config.toString()); }} |
web.xml 中加入：
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<filter> <filter-name>UserFilter</filter-name> <filter-class>com.lzw.filter.demo.UserAccessFilter</filter-class></filter><filter-mapping> <filter-name>UserFilter</filter-name> <url-pattern>/jsp/*</url-pattern></filter-mapping> |
1、攔截器是基于java的反射機(jī)制的，而過(guò)濾器是基于函數(shù)回調(diào)
2、過(guò)濾器依賴與servlet容器，而攔截器不依賴與servlet容器
3、攔截器只能對(duì)action請(qǐng)求起作用，而過(guò)濾器則可以對(duì)幾乎所有的請(qǐng)求起作用
4、攔截器可以訪問(wèn)action上下文、值棧里的對(duì)象，而過(guò)濾器不能
5、在action的生命周期中，攔截器可以多次被調(diào)用，而過(guò)濾器只能在容器初始化時(shí)被調(diào)用一次
在action的生命周期中，攔截器可以多次被調(diào)用，而過(guò)濾器只能在容器初始化時(shí)被調(diào)用一次
執(zhí)行順序 ：過(guò)濾前 - 攔截前 - Action處理 - 攔截后 - 過(guò)濾后。
個(gè)人認(rèn)為過(guò)濾是一個(gè)橫向的過(guò)程，首先把客戶端提交的內(nèi)容進(jìn)行過(guò)濾(例如未登錄用戶不能訪問(wèn)內(nèi)部頁(yè)面的處理)；
過(guò)濾通過(guò)后，攔截器將檢查用戶提交數(shù)據(jù)的驗(yàn)證，做一些前期的數(shù)據(jù)處理，接著把處理后的數(shù)據(jù)發(fā)給對(duì)應(yīng)的Action；
Action處理完成返回后，攔截器還可以做其他過(guò)程，再向上返回到過(guò)濾器的后續(xù)操作。
三、監(jiān)聽(tīng)器：Servlet的監(jiān)聽(tīng)器Listener，它是實(shí)現(xiàn)了javax.servlet.ServletContextListener接口的服務(wù)器端程序，它也是隨web應(yīng)用的啟動(dòng)而啟動(dòng)，只初始化一次，隨web應(yīng)用的停止而銷毀。
主要作用是：做一些初始化的內(nèi)容添加工作、設(shè)置一些基本的內(nèi)容、比如一些參數(shù)或者是一些固定的對(duì)象等等。
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package com.lzw.filter.demo;import javax.servlet.ServletContext;import javax.servlet.ServletContextEvent;import javax.servlet.ServletContextListener;public class InitDataListener implements ServletContextListener { private static ServletContext servletContext; public static ServletContext getServletContext() { return servletContext; } @Override public void contextInitialized(ServletContextEvent contextEvent) { servletContext = contextEvent.getServletContext(); //final ApplicationContext ctx = WebApplicationContextUtils.getWebApplicationContext(servletContext); System.out.println("服務(wù)器啟動(dòng)完畢！"); System.out.println(servletContext); } @Override public void contextDestroyed(ServletContextEvent sce) {}} |
web.xml
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<?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"> <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> <listener> <listener-class>com.lzw.filter.demo.InitDataListener</listener-class> </listener></web-app> |
控制臺(tái)結(jié)果：
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信息: Starting service Catalina2013-10-31 15:13:55 org.apache.catalina.core.StandardEngine startInternal信息: Starting Servlet Engine: Apache Tomcat/7.0.42服務(wù)器啟動(dòng)完畢！org.apache.catalina.core.ApplicationContextFacade@7966340c2013-10-31 15:13:56 org.apache.coyote.AbstractProtocol start信息: Starting ProtocolHandler ["http-apr-8080"]2013-10-31 15:13:56 org.apache.coyote.AbstractProtocol start信息: Starting ProtocolHandler ["ajp-apr-8009"]2013-10-31 15:13:56 org.apache.catalina.startup.Catalina start信息: Server startup in 402 ms |
希望本文所述對(duì)大家java程序設(shè)計(jì)有所幫助。
