1、简介
作为下一代的Web标准，HTML5拥有许多引人注目的新特性，如 Canvas、本地存储、多媒体编程接口、WebSocket等等。这其中有“Web的 TCP”之称的 WebSocket格外吸引开发人员的注意。WebSocket的出现使得浏览器提供对 Socket的支持成为可能，从而在浏览器和服务器之间提供了一个基于TCP连接的双向通道。Web开发人员可以非常方便地使用WebSocket构建实时 web 应用，开发人员的手中从此又多了一柄神兵利器。
Web 应用的信息交互过程通常是客户端通过浏览器发出一个请求，服务器端接收和审核完请求后进行处理并返回结果给客户端，然后客户端浏览器将信息呈现出来，这种机制对于信息变化不是特别频繁的应用尚能相安无事，但是对于那些实时要求比较高的应用来说，比如说在线游戏、在线证券、设备监控、新闻在线播报、RSS订阅推送等等，当客户端浏览器准备呈现这些信息的时候，这些信息在服务器端可能已经过时了。
所以保持客户端和服务器端的信息同步是实时 Web应用的关键要素，对 Web开发人员来说也是一个难题。在 WebSocket规范出来之前，开发人员想实现这些实时的Web应用，不得不采用一些折衷的方案，其中最常用的就是轮询(Polling)和 Comet 技术，而Comet技术实际上是轮询技术的改进，又可细分为两种实现方式，一种是长轮询机制，一种称为流技术。
Html5 WebSocket 设计出来的目的就是要取代轮询和 Comet技术，使客户端浏览器具备像 C/S架构下桌面系统的实时通讯能力。浏览器通过JavaScript向服务器发出建立 WebSocket连接的请求，连接建立以后，客户端和服务器端就可以通过 TCP连接直接交换数据。因为 WebSocket连接本质上就是一个TCP连接，所以在数据传输的稳定性和数据传输量的大小方面，和轮询以及Comet技术比较，具有很大的性能优势。
但是鉴于web socket 对浏览器要求比较高，为了解决这个问题，推出了sockJS，SockJS是一个JavaScript库，提供跨浏览器javascript的API，创建了一个低延迟、全双工的浏览器和web服务器之间通信通道。
2、相关环境要求
Spring4.0.6(要选择4.0+),tomcat7.0.55版本，JDK1.7。
3、具体代码
（以下代码亲测可用！）
（1）web.xml:
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<?xmlversionxmlversion="1.0"encoding="UTF-8"?> <web-app version="3.1"xmlns="http://xmlns.jcp.org/xml/ns/javaee"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd"> <description>用来测试WebSocket基础上推送的功能</description> <distributable/> <filter> <filter-name>encodingFilter</filter-name> <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class> <async-supported>true</async-supported> <init-param> <param-name>encoding</param-name> <param-value>UTF-8</param-value> </init-param> <init-param> <param-name>forceEncoding</param-name> <param-value>true</param-value> </init-param> </filter> <filter-mapping> <filter-name>encodingFilter</filter-name> <url-pattern>/*</url-pattern> </filter-mapping> <listener> <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class> </listener> <!-- Spring 刷新Introspector防止内存泄露 --> <listener> <listener-class>org.springframework.web.util.IntrospectorCleanupListener</listener-class> </listener> <servlet> <servlet-name>dispatcher</servlet-name> <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class> <init-param> <param-name>contextConfigLocation</param-name> <param-value>classpath:dispatcher-servlet.xml</param-value> </init-param> <load-on-startup>1</load-on-startup> <async-supported>true</async-supported> </servlet> <servlet-mapping> <servlet-name>dispatcher</servlet-name> <url-pattern>/</url-pattern> </servlet-mapping> <session-config> <session-timeout> 30 </session-timeout> </session-config> <welcome-file-list> <welcome-file>testSocket.jsp</welcome-file> </welcome-file-list> </web-app> |
(2) dispatcher-servlet.xml
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<?xmlversionxmlversion="1.0"encoding="UTF-8"?> <beans:beansxmlnsbeans:beansxmlns="http://www.springframework.org/schema/mvc" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:beans="http://www.springframework.org/schema/beans" xmlns:context="http://www.springframework.org/schema/context" xsi:schemaLocation="http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc.xsd http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd"> <annotation-driven/> <!-- 自动扫描的包名 --> <context:component-scanbase-packagecontext:component-scanbase-package="zyy.sockjs.config"></context:component-scan> </beans:beans> |
(3)HandshakeInterceptor.java
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package zyy.sockjs.config; import java.util.Map; import org.springframework.http.server.ServerHttpRequest; import org.springframework.http.server.ServerHttpResponse; import org.springframework.stereotype.Component; import org.springframework.web.socket.WebSocketHandler; import org.springframework.web.socket.server.support.HttpSessionHandshakeInterceptor; @Componentpublic class HandshakeInterceptor extends HttpSessionHandshakeInterceptor { @Overridepublic boolean beforeHandshake(ServerHttpRequest request, ServerHttpResponse response, WebSocketHandler wsHandler, Map<String, Object> attributes) throws Exception { System.out.println("Before Handshake"); return super.beforeHandshake(request,response,wsHandler,attributes); } @Overridepublic void afterHandshake(ServerHttpRequest request, ServerHttpResponse response, WebSocketHandler wsHandler, Exception ex) { System.out.println("After Handshake"); super.afterHandshake(request,response,wsHandler,ex); } } |
(4)InfoSocketEndPoint.Java
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package zyy.sockjs.config; import org.springframework.stereotype.Component; import org.springframework.web.socket.TextMessage; import org.springframework.web.socket.WebSocketSession; import org.springframework.web.socket.handler.TextWebSocketHandler; @Componentpublic class InfoSocketEndPoint extends TextWebSocketHandler { public InfoSocketEndPoint() { } @Overrideprotected void handleTextMessage(WebSocketSession session, TextMessage message) throws Exception { super.handleTextMessage(session, message); TextMessage returnMessage = new TextMessage(message.getPayload() + " received at server"); session.sendMessage(returnMessage); } } |
(5)SystemWebSocketHandler.java
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package zyy.sockjs.config; import org.springframework.stereotype.Component; import org.springframework.web.socket.CloseStatus; import org.springframework.web.socket.TextMessage; import org.springframework.web.socket.WebSocketHandler; import org.springframework.web.socket.WebSocketMessage; import org.springframework.web.socket.WebSocketSession; /** * * @author dayu */ @Componentpublic class SystemWebSocketHandler implements WebSocketHandler { @Override public void afterConnectionEstablished(WebSocketSession session) throws Exception { System.out.println("connect to the websocket success......"); session.sendMessage(new TextMessage("Server:connected OK!")); } @Override public void handleMessage(WebSocketSession wss, WebSocketMessage<?> wsm) throws Exception { TextMessage returnMessage = new TextMessage(wsm.getPayload() + " received at server"); wss.sendMessage(returnMessage); } @Override public void handleTransportError(WebSocketSession wss, Throwable thrwbl) throws Exception { if(wss.isOpen()){ wss.close(); } System.out.println("websocket connection closed......"); } @Override public void afterConnectionClosed(WebSocketSession wss, CloseStatus cs) throws Exception { System.out.println("websocket connection closed......"); } @Override public boolean supportsPartialMessages() { return false; } } |
(6)WebSocketConfig.java
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package zyy.sockjs.config; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration; import org.springframework.web.servlet.config.annotation.EnableWebMvc; import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter; import org.springframework.web.socket.WebSocketHandler; import org.springframework.web.socket.config.annotation.EnableWebSocket; import org.springframework.web.socket.config.annotation.WebSocketConfigurer; import org.springframework.web.socket.config.annotation.WebSocketHandlerRegistry; @Configuration@EnableWebMvc@EnableWebSocketpublic class WebSocketConfig extends WebMvcConfigurerAdapter implements WebSocketConfigurer { public WebSocketConfig() { } @Override public void registerWebSocketHandlers(WebSocketHandlerRegistry registry) { registry.addHandler(systemWebSocketHandler(), "/websck").addInterceptors(new HandshakeInterceptor()); System.out.println("registed!"); registry.addHandler(systemWebSocketHandler(), "/sockjs/websck/info").addInterceptors(new HandshakeInterceptor()) .withSockJS(); } @Bean public WebSocketHandler systemWebSocketHandler() { return new SystemWebSocketHandler(); } } |
(7)testSocket.jsp
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<%@ page language="java"contentType="text/html; charset=ISO-8859-1" pageEncoding="ISO-8859-1"%> <!DOCTYPE htmlPUBLIC"-//W3C//DTD HTML 4.01 Transitional//EN""http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type"content="text/html; charset=ISO-8859-1"> <title>WebSocket/SockJS Echo Sample (Adapted from Tomcat's echo sample)</title> <style type="text/css"> #connect-container { float: left; width: 400px } #connect-container div { padding: 5px; } #console-container { float: left; margin-left: 15px; width: 400px; } #console { border:1px solid #CCCCCC; border-right-color:#33333333; border-bottom-color:#999999; height: 170px; overflow-y: scroll; padding: 5px; width: 100%; } #console p { padding: 0; margin: 0; } </style> <script src="http://cdn.sockjs.org/sockjs-0.3.min.js"></script> <script type="text/javascript"> var ws = null; var url = null; var transports = []; function setConnected(connected) { document.getElementById('connect').disabled = connected; document.getElementById('disconnect').disabled = !connected; document.getElementById('echo').disabled = !connected; } function connect() { if (!url) { log('Select whether to use W3C WebSocket or SockJS'); return; } //ws = (url.indexOf('sockjs') != -1) ?new SockJS(url, undefined, {protocols_whitelist: transports}) : new WebSocket(url); if ('WebSocket'in window) { ws= new WebSocket("ws://localhost:8080/SpringSocketJs/websck"); }else { ws = new SockJS("http://localhost:8080/SpringSocketJs/sockjs/websck/info"); } //websocket = new SockJS("http://localhost:8084/SpringWebSocketPush/sockjs/websck"); ws.onopen = function () { setConnected(true); //log('Info: connection opened.'); }; ws.onmessage = function (event) { log('Received: ' + event.data); }; ws.onclose = function (event) { setConnected(false); log('Info: connection closed.'); log(event); }; } function disconnect() { if (ws != null) { ws.close(); ws = null; } setConnected(false); } function echo() { if (ws != null) { var message = document.getElementById('message').value; log('Sent: ' + message); ws.send(message); } else { alert('connection not established, please connect.'); } } function updateUrl(urlPath) { if (urlPath.indexOf('sockjs') != -1) { url = urlPath; document.getElementById('sockJsTransportSelect').style.visibility ='visible'; } else { if (window.location.protocol =='http:') { url = 'ws://' + window.location.host + urlPath; } else { url = 'wss://' + window.location.host + urlPath; } document.getElementById('sockJsTransportSelect').style.visibility ='hidden'; } } function updateTransport(transport) { transports = (transport == 'all') ? [] : [transport]; } function log(message) { var console = document.getElementById('console'); var p = document.createElement('p'); p.style.wordWrap = 'break-word'; p.appendChild(document.createTextNode(message)); console.appendChild(p); while (console.childNodes.length > 25) { console.removeChild(console.firstChild); } console.scrollTop = console.scrollHeight; } </script> </head> <body> <noscript><h2 style="color:#ff0000">Seems your browser doesn't supportJavascript!Websockets rely on Javascript being enabled. Please enable Javascript and reload this page!</h2></noscript> <div> <div id="connect-container"> <input id="radio1"type="radio"name="group1"onclick="updateUrl('/SpringSocketJs/websocket');"> <label for="radio1">W3C WebSocket</label> <br> <input id="radio2"type="radio"name="group1"onclick="updateUrl('/SpringSocketJs/sockjs/websocket');"> <label for="radio2">SockJS</label> <div id="sockJsTransportSelect" style="visibility:hidden;"> SockJS transport: <select onchange="updateTransport(this.value)"> <option value="all">all</option> <option value="websocket">websocket</option> <option value="xhr-polling">xhr-polling</option> <option value="jsonp-polling">jsonp-polling</option> <option value="xhr-streaming">xhr-streaming</option> <option value="iframe-eventsource">iframe-eventsource</option> <option value="iframe-htmlfile">iframe-htmlfile</option> </select> </div> <div> <button id="connect"onclick="connect();">Connect</button> <button id="disconnect"disabled="disabled"onclick="disconnect();">Disconnect</button> </div> <div> <textarea id="message"style="width:350px">Here is a message!</textarea> </div> <div> <button id="echo"onclick="echo();"disabled="disabled">Echo message</button> </div> </div> <div id="console-container"> <div id="console"></div> </div> </div> </body> </html> |
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持服务器之家。
原文链接：http://blog.csdn.net/u011991249/article/details/51472020
