本文主要有三个步骤

1、用户登录后建立websocket连接，默认选择websocket连接，如果浏览器不支持，则使用sockjs进行模拟连接
2、建立连接后，服务端返回该用户的未读消息
3、服务端进行相关操作后，推送给某一个用户或者所有用户新消息 相关环境 Spring4.0.6(要选择4.0+),tomcat7.0.55

Websocet服务端实现

WebSocketConfig.java

@Configuration@EnableWebMvc@EnableWebSocketpublic class WebSocketConfig extends WebMvcConfigurerAdapter implements WebSocketConfigurer {@Overridepublic void registerWebSocketHandlers(WebSocketHandlerRegistry registry) {registry.addHandler(systemWebSocketHandler(),"/webSocketServer").addInterceptors(new WebSocketHandshakeInterceptor());registry.addHandler(systemWebSocketHandler(), "/sockjs/webSocketServer").addInterceptors(new WebSocketHandshakeInterceptor()).withSockJS();}@Beanpublic WebSocketHandler systemWebSocketHandler(){return new SystemWebSocketHandler();}}

不要忘记在springmvc的配置文件中配置对此类的自动扫描

<context:component-scan base-package="com.ldl.origami.websocket" />

@Configuration
@EnableWebMvc
@EnableWebSocket

这三个大致意思是使这个类支持以@Bean的方式加载bean，并且支持springmvc和websocket，不是很准确大致这样，试了一下@EnableWebMvc不加也没什么影响，@Configuration本来就支持springmvc的自动扫描

registry.addHandler(systemWebSocketHandler(),"/webSocketServer").addInterceptors(new WebSocketHandshakeInterceptor())

用来注册websocket server实现类，第二个参数是访问websocket的地址

registry.addHandler(systemWebSocketHandler(), "/sockjs/webSocketServer").addInterceptors(new WebSocketHandshakeInterceptor()).withSockJS();}

这个是使用Sockjs的注册方法

首先SystemWebSocketHandler.java

public class SystemWebSocketHandler implements WebSocketHandler {private static final Logger logger;private static final ArrayList<WebSocketSession> users;static {users = new ArrayList<>();logger = LoggerFactory.getLogger(SystemWebSocketHandler.class);}@Autowiredprivate WebSocketService webSocketService;@Overridepublic void afterConnectionEstablished(WebSocketSession session) throws Exception {logger.debug("connect to the websocket success......");users.add(session);String userName = (String) session.getAttributes().get(Constants.WEBSOCKET_USERNAME);if(userName!= null){//查询未读消息int count = webSocketService.getUnReadNews((String) session.getAttributes().get(Constants.WEBSOCKET_USERNAME));session.sendMessage(new TextMessage(count + ""));}}@Overridepublic void handleMessage(WebSocketSession session, WebSocketMessage<?> message) throws Exception {//sendMessageToUsers();}@Overridepublic void handleTransportError(WebSocketSession session, Throwable exception) throws Exception {if(session.isOpen()){session.close();}logger.debug("websocket connection closed......");users.remove(session);}@Overridepublic void afterConnectionClosed(WebSocketSession session, CloseStatus closeStatus) throws Exception {logger.debug("websocket connection closed......");users.remove(session);}@Overridepublic boolean supportsPartialMessages() {return false;}/*** 给所有在线用户发送消息** @param message*/public void sendMessageToUsers(TextMessage message) {for (WebSocketSession user : users) {try {if (user.isOpen()) {user.sendMessage(message);}} catch (IOException e) {e.printStackTrace();}}}/*** 给某个用户发送消息** @param userName* @param message*/public void sendMessageToUser(String userName, TextMessage message) {for (WebSocketSession user : users) {if (user.getAttributes().get(Constants.WEBSOCKET_USERNAME).equals(userName)) {try {if (user.isOpen()) {user.sendMessage(message);}} catch (IOException e) {e.printStackTrace();}break;}}}}

相关内容大家一看就能明白，就不多解释了

然后WebSocketHandshakeInterceptor.java

public class WebSocketHandshakeInterceptor implements HandshakeInterceptor {private static Logger logger = LoggerFactory.getLogger(HandshakeInterceptor.class);@Overridepublic boolean beforeHandshake(ServerHttpRequest request, ServerHttpResponse response, WebSocketHandler wsHandler, Map<String, Object> attributes) throws Exception {if (request instanceof ServletServerHttpRequest) {ServletServerHttpRequest servletRequest = (ServletServerHttpRequest) request;HttpSession session = servletRequest.getServletRequest().getSession(false);if (session != null) {//使用userName区分WebSocketHandler，以便定向发送消息String userName = (String) session.getAttribute(Constants.SESSION_USERNAME);attributes.put(Constants.WEBSOCKET_USERNAME,userName);}}return true;}@Overridepublic void afterHandshake(ServerHttpRequest request, ServerHttpResponse response, WebSocketHandler wsHandler, Exception exception) {}}

这个的主要作用是取得当前请求中的用户名，并且保存到当前的WebSocketHandler中，以便确定WebSocketHandler所对应的用户，具体可参考HttpSessionHandshakeInterceptor

用户登录建立websocket连接

index.jsp

<script type="text/javascript" src="http://localhost:8080/Origami/websocket/sockjs-0.3.min.js"></script><script>var websocket;if ('WebSocket' in window) {websocket = new WebSocket("ws://localhost:8080/Origami/webSocketServer");} else if ('MozWebSocket' in window) {websocket = new MozWebSocket("ws://localhost:8080/Origami/webSocketServer");} else {websocket = new SockJS("http://localhost:8080/Origami/sockjs/webSocketServer");}websocket.onopen = function (evnt) {};websocket.onmessage = function (evnt) {$("#msgcount").html("(<font color='red'>"+evnt.data+"</font>)")};websocket.onerror = function (evnt) {};websocket.onclose = function (evnt) {}</script>

使用sockjs时要注意

1、这两个的写法

<script type="text/javascript" src="http://localhost:8080/Origami/websocket/sockjs-0.3.min.js"></script>websocket = new SockJS(http://localhost:8080/Origami/sockjs/webSocketServer);

2、web.xml中

<web-app version="3.0" xmlns="http://java.sun.com/xml/ns/javaee"xmlns:xsi="http://.fasterxml.jackson.core</groupId><artifactId>jackson-databind</artifactId><version>2.3.3</version></dependency>

好了，现在websocket可以正常建立起来了

返回用户未读的消息

当连接建立后，会进入SystemWebSocketHandler的afterConnectionEstablished方法，代码看上边，取出WebSocketHandshakeInterceptor中保存的用户名

查询信息后使用session.sendMessage(new TextMessage(count + ""));返回给用户，从哪来回哪去

服务端推送消息给用户

@Controllerpublic class AdminController {static Logger logger = LoggerFactory.getLogger(AdminController.class);@Autowired(required = false)private AdminService adminService;@Beanpublic SystemWebSocketHandler systemWebSocketHandler() {return new SystemWebSocketHandler();}@RequestMapping("/auditing")@ResponseBodypublic String auditing(HttpServletRequest request){//无关代码都省略了int unReadNewsCount = adminService.getUnReadNews(username);systemWebSocketHandler().sendMessageToUser(username, new TextMessage(unReadNewsCount + ""));return result;}}

在这里可以使用sendMessageToUser给某个用户推送信息，也可以使用sendMessageToUsers给所有用户推送信息