WebSocket錯誤：java.lang.IllegalStateException: The WebSocket session [1] has been closed and no method (apart from close()) may be called on a closed session

　主要原因：在建立連接存儲對象信息的時候保存了用戶ID，在斷開連接時移除當前對象失敗。

private static CopyOnWriteArraySet<AcceptWebSocket> webSocketSet = new CopyOnWriteArraySet<>();

@OnOpen

public void onOpen(@PathParam("userid") Integer id, Session session) {

    this.session = session;
    this.userid = id;
    webSocketSet.put(userid, this);//用戶id 和session綁定
    logger.info("【新的socket連接】");
}

修改：通過判斷所有登錄的用戶是否屬於當前用戶組，實現單發或者群發。

/**
 * 打開連接時
 *
 * @param session
 */
@OnOpen
public void onOpen(@PathParam("userid") Integer userid, Session session) {
    this.session = session;
    this.work = userService.selectUserId(userid);
    webSocketSet.add(this);
    logger.info("【新的socket連接】");
}

/**
 * 向所有連接客戶端推送消息
 */
public  void sendWebSocketMessage(String message) {
    try {
        if (webSocketSet.size() != 0) {
            for (AcceptWebSocket p : webSocketSet) {
                if (p != null && p.work == 3) {
                    p.session.getBasicRemote().sendText(message);
                }
            }
        }
    } catch (IOException e) {
        e.printStackTrace();
    }
}

/**
 * 關閉連接時
 */
@OnClose
public void onClose() {
    webSocketSet.remove(this);
    logger.info("【socket連接關閉】");
}