springMVC+spring+MyBatis+websocket技术整合

websocket是目前唯一真正实现全双工通信的服务器向客户端推的互联网技术，与长连接和轮询技术相比，websocket的优越性不言自明，长连接的连接资源（线程资源）随着连接数量的增多，必会耗尽，客户端轮询会给服务器造成很大的压力，而websocket是在物理层非网络层建立一条客户端至服务器的长连接，以此来保证服务器向客户端的即时推送，既不耗费线程资源，又不会不断向服务器轮询请求。

下面言归正传，讲一讲SSM（springMVC+spring+MyBatis）框架中集成websocket技术的曲折蛋疼直至成功喜悦之路。

1 在maven的pom.xml中加入websocket所依赖的jar包，什么，你不知道maven，快去度之或者查看撸主关于maven的博文恶补一下，spring-websocket所依赖的jar包有以下几个：

<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>3.1.0</version>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-core</artifactId>
<version>2.3.0</version>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>2.3.0</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-websocket</artifactId>
<version>4.0.1.RELEASE</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-messaging</artifactId>
<version>4.0.1.RELEASE</version>
</dependency>

2 更新web.xml中namespace.xsd的版本
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:websocket="http://www.springframework.org/schema/websocket"
xsi:schemaLocation=" http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/websocket http://www.springframework.org/schema/websocket/spring-websocket.xsd">

3 更新spring框架的jar包至4.0以上（spring-core, spring-context, spring-web and spring-webmvc）
<dependency>
<span style="white-space:pre"> </span><groupId>org.springframework</groupId>
<artifactId>spring-core</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-web</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-webmvc</artifactId>
<version>${spring.version}</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context-support</artifactId>
<version>${spring.version}</version>
</dependency>

4 创建websocket处理类
package com.up.websocket.handler;

import org.springframework.web.socket.TextMessage;
import org.springframework.web.socket.WebSocketSession;
import org.springframework.web.socket.handler.TextWebSocketHandler;

public class WebsocketEndPoint extends TextWebSocketHandler {

@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 创建握手（handshake）接口
package com.up.websocket;

import java.util.Map;

import org.springframework.http.server.ServerHttpRequest;
import org.springframework.http.server.ServerHttpResponse;
import org.springframework.web.socket.WebSocketHandler;
import org.springframework.web.socket.server.support.HttpSessionHandshakeInterceptor;

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);
}

}

6 处理类和握手协议的spring配置(applicationContext.xml文件）
<bean id="websocket" class="com.up.websocket.handler.WebsocketEndPoint"/>

<websocket:handlers>
<websocket:mapping path="/websocket" handler="websocket"/>
<websocket:handshake-interceptors>
<bean class="com.up.websocket.HandshakeInterceptor"/>
</websocket:handshake-interceptors>
</websocket:handlers>

7 客户端页面
<!DOCTYPE html>
<html>
<head>
<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: #999999;
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() {
alert("url:"+url);
if (!url) {
alert('Select whether to use W3C WebSocket or SockJS');
return;
}

ws = (url.indexOf('sockjs') != -1) ?
new SockJS(url, undefined, {protocols_whitelist: transports}) : new WebSocket(url);

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) {
alert(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 support Javascript! 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(''/spring-websocket-uptest/websocket');">
<label for="radio1">W3C WebSocket</label>
<br>
<input id="radio2" type="radio" name="group1" onclick="updateUrl('/spring-websocket-uptest/websocket');">
<label for="radio2">SockJS</label>
<div id="sockJsTransportSelect" style="visibility:hidden;">
<span>SockJS transport:</span>
<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>

7 按照以上步骤搭建，根据个人开发环境不同，可能会出现各种问题
org.apache.tomcat.websocket.server.WsServerContainer cannot be cast to javax.websocket.server

严重: Servlet.service() for servlet [SpringMVC] in context with path [/ZHDM] threw exception [Request processing failed; nested exception is org.springframework.web.socket.server.HandshakeFailureException: Uncaught failure for request http://125.221.225.118:8080/ZHDM/websocket; nested exception is java.lang.ClassCastException: org.apache.tomcat.websocket.server.WsServerContainer cannot be cast to javax.websocket.server.ServerContainer] with root cause
java.lang.ClassCastException: org.apache.tomcat.websocket.server.WsServerContainer cannot be cast to javax.websocket.server.ServerContainer
at org.springframework.web.socket.server.standard.AbstractStandardUpgradeStrategy.getContainer(AbstractStandardUpgradeStrategy.java:76)
at org.springframework.web.socket.server.standard.TomcatRequestUpgradeStrategy.getContainer(TomcatRequestUpgradeStrategy.java:85)
at org.springframework.web.socket.server.standard.TomcatRequestUpgradeStrategy.getContainer(TomcatRequestUpgradeStrategy.java:47)
at org.springframework.web.socket.server.standard.AbstractStandardUpgradeStrategy.getSupportedExtensions(AbstractStandardUpgradeStrategy.java:68)
at org.springframework.web.socket.server.support.DefaultHandshakeHandler.doHandshake(DefaultHandshakeHandler.java:206)
at org.springframework.web.socket.server.support.WebSocketHttpRequestHandler.handleRequest(WebSocketHttpRequestHandler.java:120)
at org.springframework.web.servlet.mvc.HttpRequestHandlerAdapter.handle(HttpRequestHandlerAdapter.java:51)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:945)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:876)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:961)
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:852)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:618)
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:837)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:725)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:301)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:108)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:503)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:136)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:74)
at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:610)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:516)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1015)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:652)
at org.apache.coyote.http11.Http11AprProtocol$Http11ConnectionHandler.process(Http11AprProtocol.java:277)
at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.doRun(AprEndpoint.java:2451)
at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2440)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:744)

解决方案：

出现这个问题的原因是，apache的websocket包和javax-servlet包冲突了，找到Apache Tomcat的webApp目录，打开你部署的项目文件夹，依次打开WEB-INF/lib，找到javaee-api-7.0.jar，删除，再重新启动项目。
原博有示例代码下载：http://download.csdn.net/detail/up19910522/9192447

转自【http://blog.csdn.net/gisredevelopment/article/details/38392629】