WebSocket是HTML5提出的一个用于通信的协议规范，该协议通过一个握手机制，在客户端和服务端之间建立一个类似于TCP的连接，从而方便客户端和服务端之间的通信。
WebSocket协议本质上是一个基于TCP的协议，是先通过HTTP/HTTPS协议发起一条特殊的HTTP请求进行握手后创建一个用于交换数据的TCP连接，此后服务端与客户端通过此TCP连接进行实时通信。客户端和服务端只需要要做一个握手的动作，在建立连接之后，服务端和客户端之间就可以通过此TCP连接进行实时通信。
websocket是建立在物理层上的连接，相比于基于网络层的长连接可以节约资源，相比于AJAX轮训可以降低服务器压力。
spring在4.0后将websocket集成进去，要使用spring的websocket的话，spring的版本要在4.0及以上。
spring使用websocket需要的jar（pom.xml）
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-websocket</artifactId>
<version>4.0.6.RELEASE</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-messaging</artifactId>
<version>4.0.6.RELEASE</version>
</dependency>
web.xml中对websocket的配置
<servlet>
<servlet-name>springMVC</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:/springMVC/spring-webSocket.xml</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
<async-supported>true</async-supported>
</servlet>
<servlet-mapping>
<servlet-name>springMVC</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
springMVC中对websocket的xml配置
<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-4.0.xsd
http://www.springframework.org/schema/websocket
http://www.springframework.org/schema/websocket/spring-websocket-4.0.xsd"> <!-- websocket处理类 -->
<bean id="msgHandler" class="com.test.websocket.MyWebSocketHandler" />
<!-- 握手接口/拦截器 ，看项目需求是否需要-->
<bean id="handshakeInterceptor" class="com.test.websocket.MyHandshakeInterceptor" />
<websocket:handlers>
<websocket:mapping path="/websocket" handler="msgHandler" />
<websocket:handshake-interceptors>
<ref bean="handshakeInterceptor" />
</websocket:handshake-interceptors>
</websocket:handlers>
<!-- 注册 sockJS,sockJs是spring对不能使用websocket协议的客户端提供一种模拟 -->
<websocket:handlers>
<websocket:mapping path="/sockjs/websocket" handler="msgHandler" />
<websocket:handshake-interceptors>
<ref bean="handshakeInterceptor" />
</websocket:handshake-interceptors>
<websocket:sockjs />
</websocket:handlers>
</beans>
springMVC中对websocket的注解配置
@Configuration
@EnableWebSocket
public class WebSocketServerConfig implements WebSocketConfigurer { @Override
public void registerWebSocketHandlers(WebSocketHandlerRegistry registry) {
// 添加拦截地址以及相应的websocket消息处理器
WebSocketHandlerRegistration registration = registry.addHandler(new MyWebSocketHandler(), "/websocket","sockjs/websocket");
SockJsServiceRegistration sockJS = registration.withSockJS();
// 添加拦截器
registration.addInterceptors(new MyHandshakeInterceptor());
} }
握手拦截器，继承HttpSessionHandshakeInterceptor类，做一些连接握手或者握手后的一些处理
public class MyHandshakeInterceptor extends HttpSessionHandshakeInterceptor {
// 握手前
@Override
public boolean beforeHandshake(ServerHttpRequest request,
ServerHttpResponse response, WebSocketHandler wsHandler,
Map<String, Object> attributes) throws Exception {
System.out
.println("++++++++++++++++ HandshakeInterceptor: beforeHandshake ++++++++++++++"
+ attributes);
return super.beforeHandshake(request, response, wsHandler, attributes);
}
// 握手后
@Override
public void afterHandshake(ServerHttpRequest request,
ServerHttpResponse response, WebSocketHandler wsHandler,
Exception ex) {
System.out
.println("++++++++++++++++ HandshakeInterceptor: afterHandshake ++++++++++++++");
super.afterHandshake(request, response, wsHandler, ex);
}
}创建MyWebSocketHandler类继承WebSocketHandler类（Spring提供的有AbstractWebSocketHandler类、TextWebSocketHandler类、BinaryWebSocketHandler类，看自己需要进行继承），该类主要是用来处理消息的接收和发送
public class MyWebSocketHandler implements WebSocketHandler {
private Logger logger = LoggerFactory.getLogger(MsgWebSocketHandler.class);
//保存用户链接
private static ConcurrentHashMap<String, WebSocketSession> users = new ConcurrentHashMap<String, WebSocketSession>();
// 连接 就绪时
@Override
public void afterConnectionEstablished(WebSocketSession session)
throws Exception {
users.put(session.getId(), session);
}
// 处理信息
@Override
public void handleMessage(WebSocketSession session,
WebSocketMessage<?> message) throws Exception {
System.err.println(session + "---->" + message + ":"+ message.getPayload().toString());
}
// 处理传输时异常
@Override
public void handleTransportError(WebSocketSession session,
Throwable exception) throws Exception {
}
// 关闭 连接时
@Override
public void afterConnectionClosed(WebSocketSession session,
CloseStatus closeStatus) {
logger.debug("用户： " + session.getRemoteAddress() + " is leaving, because:" + closeStatus);
}
//是否支持分包
@Override
public boolean supportsPartialMessages() {
return false;
}
}要进行发送消息的操作，自己可以写方法，利用保存的已经完成连接的WebSocketSession，通过调用sendMessage(WebScoketMessage<?> message)方法进行消息的发送，参数message是发送的消息内容，Spring提供的类型有TextMessage、BinaryMessage、PingMessage、PongMessage。
前端客户端JS
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>websocket</title>
</head>
<style type="text/css">
#div {
color: red;
}
</style>
<body>
<h1>WEBSOCKET----TEST</h1>
<div id="div"> </div>
</script>
<script type="text/javascript">
var div = document.getElementById('div');
var socket = new WebSocket('ws://127.0.0.1:8088/websocket'); socket.onopen = function(event){
console.log(event);
socket.send('websocket client connect test');
} socket.onclose = function(event){
console.log(event);
} socket.onerror = function(event){
console.log(event);
} socket.onmessage = function(event){
console.log(event)
div.innerHTML += (' @_@ ' + event.data + ' ~_~ ');
}
</script>
</body>
</html>
其实在后台也可以进行websocket客户端的创建
@Test
public void connectTest(){
WsWebSocketContainer wsWebSocketContainer = new WsWebSocketContainer();
wsWebSocketContainer.setDefaultMaxSessionIdleTimeout(300);
StandardWebSocketClient client = new StandardWebSocketClient(wsWebSocketContainer);
WebSocketHandler webSocketHandler = new MyWebSocketHandler();
String uriTemplate = "ws://127.0.0.1:8088/websocket?account=11111";
Object uriVars = null;
ListenableFuture<WebSocketSession> future = client.doHandshake(webSocketHandler, uriTemplate, uriVars);
try {
WebSocketSession session = future.get();
session.sendMessage(new TextMessage("hello world"));
} catch (InterruptedException | ExecutionException | IOException e) {
e.printStackTrace();
} } @Test
public void connectTest2(){
StandardWebSocketClient client = new StandardWebSocketClient();
WebSocketHandler webSocketHandler = new MyWebSocketHandler();
String uriTemplate = "ws://127.0.0.1:8088/websocket";
UriComponentsBuilder fromUriString = UriComponentsBuilder.fromUriString(uriTemplate);
fromUriString.queryParam("account","111111");
/*
* 作用同上，都是将请求参数填入到URI中
* MultiValueMap<String, String> params = new LinkedMultiValueMap<String, String>();
* params.add("account","111111");
* fromUriString.queryParams(params);
* */
URI uri = fromUriString.buildAndExpand().encode().toUri();
WebSocketHttpHeaders headers = null;
ListenableFuture<WebSocketSession> doHandshake = client.doHandshake(webSocketHandler, headers , uri);
try {
WebSocketSession session = doHandshake.get();
session.sendMessage(new TextMessage("hello world"));
} catch (InterruptedException | ExecutionException | IOException e) {
e.printStackTrace();
} }
这是我利用Junit进行的测试，实验证明是可以完成websocket的连接。
注意：websocket在进行连接的时候是可以类似get请求一样，将参数拼接到url中。还可以自己将参数封装进URI中，利用另一个方法进行连接的握手操作。