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详解WebSocket+spring示例demo（已使用sockJs库）

分类: IT文章 • 2022-04-12 09:00:48

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>

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。

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