@Configuration
public class WebSocketConfig {
　　
  @Bean(name="serverEndpointExporter")
  public ServerEndpointExporter getServerEndpointExporterBean(){
    return new ServerEndpointExporter();
  }
}

@Component
@ServerEndpoint(value = "/messageSocket/{userId}")
public class MessageWebSocket {
  private static final Logger logger = LoggerFactory.getLogger(MessageWebSocket.class);
  /**
   * 靜態(tài)變量，用來記錄當前在線連接數(shù)。應該把它設計成線程安全的。
   */
  private static int onlineCount = 0;
  /**
   * key: userId value: sessionIds
   */
  private static ConcurrentHashMap<Integer, ConcurrentLinkedQueue<String>> userSessionMap = new ConcurrentHashMap<>();
  /**
   * concurrent包的線程安全Map，用來存放每個客戶端對應的MyWebSocket對象。
   */
  private static ConcurrentHashMap<String, MessageWebSocket> websocketMap = new ConcurrentHashMap<>();
  /**
   * key: sessionId value: userId
   */
  private static ConcurrentHashMap<String, Integer> sessionUserMap = new ConcurrentHashMap<>();
  /**
   * 當前連接會話，需要通過它來給客戶端發(fā)送數(shù)據(jù)
   */
  private Session session;
  /**
   * 連接建立成功調(diào)用的方法
   * */
  @OnOpen
  public void onOpen(Session session, @PathParam("userId") Integer userId) {
    System.out.println(applicationContext);
    try {
      this.session = session;
      String sessionId = session.getId();
      //建立userId和sessionId的關(guān)系
      if(userSessionMap.containsKey(userId)) {
        userSessionMap.get(userId).add(sessionId);
      }else{
        ConcurrentLinkedQueue<String> queue = new ConcurrentLinkedQueue<>();
        queue.add(sessionId);
        userSessionMap.put(userId, queue);
      }
      sessionUserMap.put(sessionId, userId);
      //建立sessionId和websocket引用的關(guān)系
      if(!websocketMap.containsKey(sessionId)){
        websocketMap.put(sessionId, this);
        addOnlineCount();      //在線數(shù)加1
      }
    }catch (Exception e){
      logger.error("連接失敗");
      String es = ExceptionUtils.getFullStackTrace(e);
      logger.error(es);
    }
  }
  /**
   * 連接關(guān)閉調(diào)用的方法
   */
  @OnClose
  public void onClose() {
    String sessionId = this.session.getId();
    //移除userId和sessionId的關(guān)系
    Integer userId = sessionUserMap.get(sessionId);
    sessionUserMap.remove(sessionId);
    if(userId != null) {
      ConcurrentLinkedQueue<String> sessionIds = userSessionMap.get(userId);
      if(sessionIds != null) {
        sessionIds.remove(sessionId);
        if (sessionIds.size() == 0) {
          userSessionMap.remove(userId);
        }
      }
    }
    //移除sessionId和websocket的關(guān)系
    if (websocketMap.containsKey(sessionId)) {
      websocketMap.remove(sessionId);
      subOnlineCount();      //在線數(shù)減1
    }
  }
  /**
   * 收到客戶端消息后調(diào)用的方法
   *
   * @param messageStr 客戶端發(fā)送過來的消息
   **/
  @OnMessage
  public void onMessage(String messageStr, Session session, @PathParam("userId") Integer userId) throws IOException {
  }
  /**
   *
   * @param session
   * @param error 當連接發(fā)生錯誤時的回調(diào)
   */
  @OnError
  public void onError(Session session, Throwable error) {
    String es = ExceptionUtils.getFullStackTrace(error);
    logger.error(es);
  }
  /**
   * 實現(xiàn)服務器主動推送
   */
  public void sendMessage(String message, Integer toUserId) throws IOException {
    if(toUserId != null && !StringUtil.isEmpty(message.trim())){
      ConcurrentLinkedQueue<String> sessionIds = userSessionMap.get(toUserId);
      if(sessionIds != null) {
        for (String sessionId : sessionIds) {
          MessageWebSocket socket = websocketMap.get(sessionId);
          socket.session.getBasicRemote().sendText(message);
        }
      }
    }else{
      logger.error("未找到接收用戶連接，該用戶未連接或已斷開");
    }
  }
  public void sendMessage(String message, Session session) throws IOException {
    session.getBasicRemote().sendText(message);
  }
   /**
  *獲取在線人數(shù)
  */
  public static synchronized int getOnlineCount() {
    return onlineCount;
  }
   /**
  *在線人數(shù)加一
  */
  public static synchronized void addOnlineCount() {
    MessageWebSocket.onlineCount++;
  }
  /**
  *在線人數(shù)減一
  */
  public static synchronized void subOnlineCount() {
    MessageWebSocket.onlineCount--;
  }
}

//websocket連接實例
let websocket = null;
//初始話websocket實例
function initWebSocket(userId) {
  // ws地址 -->這里是你的請求路徑
  let host = urlConfig.wsUrl + 'messageSocket/' + userId;
  if ('WebSocket' in window) {
    websocket = new ReconnectingWebSocket(host);
    // 連接錯誤
    websocket.onerror = function () {
    }
    // 連接成功
    websocket.onopen = function () {
    }
    // 收到消息的回調(diào)，e.data為收到的信息
    websocket.onmessage = function (e) {
    }
    // 連接關(guān)閉的回調(diào)
    websocket.onclose = function () {
    }
    //監(jiān)聽窗口關(guān)閉事件，當窗口關(guān)閉時，主動去關(guān)閉websocket連接，防止連接還沒斷開就關(guān)閉窗口，server端會拋異常。
    window.onbeforeunload = function () {
      closeWebSocket();
    }
  } else {
    alert('當前瀏覽器不支持websocket')
    return;
  }
}
//關(guān)閉WebSocket連接
function closeWebSocket() {
  websocket.close();
}
//發(fā)送消息
function sendMessage(message){
  websocket.send(message);
}