详解WebSocket+spring示例demo（已使用sockJs库）

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:

<?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

<?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

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; 

@Component
public class HandshakeInterceptor extends HttpSessionHandshakeInterceptor {
@Override
public 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);
} 

@Override
public void afterHandshake(ServerHttpRequest request,
 ServerHttpResponse response, WebSocketHandler wsHandler,
 Exception ex) {
 System.out.println("After Handshake");
 super.afterHandshake(request,response,wsHandler,ex);
}
}

(4)InfoSocketEndPoint.Java

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; 

@Component
public class InfoSocketEndPoint extends TextWebSocketHandler {
public InfoSocketEndPoint() {
} 

@Override
protected 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

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
*/ 

@Component
public 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

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
@EnableWebSocket
public 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

<%@ 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>

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