java - WebSocket远程端点处于状态[TEXT_PARTIAL_WRITING]

我正在使用tomcat 8.0.15， Spring 4.1.5。

我实现了如下3种使用websocket的强制性功能。
非常简单

private Map<String, WebSocketSession> map_users = new ConcurrentHashMap<>();
private Map<String, String> map_id = new ConcurrentHashMap<>();

public void afterConnectionEstablished(WebSocketSession wss) throws Exception {
    map_users.put(wss.getId(), wss);
}

public void afterConnectionClosed(WebSocketSession wss, CloseStatus cs) throws Exception {
    map_users.remove(wss.getId());

    // remove user
    String username = map_id.get(wss.getId());
    if (username != null) {
        map_id.remove(wss.getId());
        map_id.remove(username);
    }
}

public void handleTextMessage(WebSocketSession wss, TextMessage tm) throws Exception {
    String str = tm.getPayload();
    String username = ...;

    // regist user
    if (!map_id.get(wss.getId())) {
        map_id.put(wss.getId(), username);
        map_id.put(username, wss.getId());
    }

    for (WebSocketSession w: map_users.values()) {
        w.sendMessage(new TextMessage(wss.getId() + " send to " + w.getId() + ", msg:" + tm.getPayload()));
    }
}

一些客户端发送消息，而其他客户端通过handleTextMessage获取消息。

就我而言，如果没有handleTextMessage函数，则服务器程序希望向客户端发送文本消息。
(为此，我将WebSocketSession的ID和用户名保存到map_id中)

String websocketsesssion_id = map_id.get(username);
WebSocketSession wss = map_users.get(websocketsesssion_id);
wss.sendMessage(new TextMessage(new java.util.Date()));

上面的代码效果很好。
但是，当某些客户端的WebSocketSession在使用中并尝试同时使用时，会出错。
它的意思是
1.一些客户端发送消息-> handleTextMessage被调用->客户端的WebSocketSession正在使用
2.服务器程序希望向该客户端发送消息->从 map 获取客户端的WebSocketSession->尝试使用相同的WebSocketSession发送消息

Stacktrace:] with root cause
java.lang.IllegalStateException: The remote endpoint was in state [TEXT_PARTIAL_WRITING] which is an invalid state for called method
    at org.apache.tomcat.websocket.WsRemoteEndpointImplBase$StateMachine.checkState(WsRemoteEndpointImplBase.java:1092)
    at org.apache.tomcat.websocket.WsRemoteEndpointImplBase$StateMachine.textPartialStart(WsRemoteEndpointImplBase.java:1050)
    at org.apache.tomcat.websocket.WsRemoteEndpointImplBase.sendPartialString(WsRemoteEndpointImplBase.java:218)
    at org.apache.tomcat.websocket.WsRemoteEndpointBasic.sendText(WsRemoteEndpointBasic.java:49)
    at org.springframework.web.socket.adapter.standard.StandardWebSocketSession.sendTextMessage(StandardWebSocketSession.java:197)
    at org.springframework.web.socket.adapter.AbstractWebSocketSession.sendMessage(AbstractWebSocketSession.java:105)
    at org.springframework.web.socket.sockjs.transport.session.WebSocketServerSockJsSession.writeFrameInternal(WebSocketServerSockJsSession.java:222)
    at org.springframework.web.socket.sockjs.transport.session.AbstractSockJsSession.writeFrame(AbstractSockJsSession.java:325)
    at org.springframework.web.socket.sockjs.transport.session.WebSocketServerSockJsSession.sendMessageInternal(WebSocketServerSockJsSession.java:212)
    at org.springframework.web.socket.sockjs.transport.session.AbstractSockJsSession.sendMessage(AbstractSockJsSession.java:161)

结果，WebSocketSession被关闭，客户端必须再次打开新的WebSocketSession。

所以，我的问题是:

是否可以检查WebSocketSession是否正在使用？
(在handleTextMessage函数之外)

最佳答案

问题是几个线程试图同时在套接字上写:

尝试 :

String websocketsesssion_id = map_id.get(username);
WebSocketSession wss = map_users.get(websocketsesssion_id);
synchronized(wss) {
 wss.sendMessage(new TextMessage(new java.util.Date()));
}