Java Websocket / MessageHandler return 到全局范围？

Question

我遇到了以下问题，但我还没有找到可行的解决方案。我有 3 个不同的应用程序应该相互通信：

UI 部分 (1)
后台应用（二）
微服务"in the cloud" (3)

后端应用程序为 UI 提供 Web 服务 (REST)，以获取和放置信息 from/to 微服务。我想从微服务中获取的一切都可以正常工作，但是：如果我想将数据放入微服务，规范需要一个 websocket 连接。这也可以正常工作，但是微服务 return 在（未）成功的命令之后发送一条消息，例如

{"statusCode":200,"messageId":"1234567890"}

现在的问题是：如何在我的应用程序中获取此消息并将其发送回 UI，以便用户知道命令是否成功？

目前我试过这个：

WebSocketClient.java

@OnMessage
public void onMessage(Session session, String msg) {
    if (this.messageHandler != null) {
        this.messageHandler.handleMessage(msg);
    }
}
public void addMessageHandler(MessageHandler msgHandler) {
    this.messageHandler = msgHandler;
}
public static interface MessageHandler {

    public String handleMessage(String message);
}

MyTotalAwesomeController.java

public class MyTotalAwesomeController {

    WebSocketClient wsc = new WebSocketClient();
    ...


    @RequestMapping(value="/add", method={RequestMethod.POST, RequestMethod.OPTIONS})
    public ResponseEntity<Object> putDataToMicroservice(@RequestBody Map<String, Object> payload, @RequestHeader(value = "authorization") String authorizationHeader) throws Exception {
    ...

    wsc.addMessageHandler(new WebSocketClient.MessageHandler() {
        public String handleMessage(String message) {

            System.out.println("RETURN MSG FROM WSS : " + message);
            return message;
        }
    });

    return ResponseEntity.ok("worked");
}

我可以看到 MessageHandler return 的控制台输出，但我不知道如何将它传递给 return 的父方法而不是 returning ResponseEntity.ok().

我还不太习惯 Java 中的 WebSocket 连接，所以请不要评判我 ;-)

感谢您的帮助。

Answer 1

下面的代码将假设 @OnMessage 方法在 WebSocket 客户端运行时管理的线程中执行。请检查运行 @OnMessage 方法的线程。

如果上述前提为真，putDataToMicroservice()方法，由全局范围内的线程执行，会一直等到WebSocket响应到达WS客户端线程，WS客户端线程会将消息重新传递给全局范围线程。然后在你的控制器中执行 class 将继续。

public class MyTotalAwesomeController {

    WebSocketClient wsc = new WebSocketClient();

    // Queue for communication between threads.
    private BlockingQueue<String> queue;

    @PostConstruct
    void init() {

        queue = new SynchronousQueue<>(true);

        // This callback will be invoked by the WebSocket thread.
        wsc.addMessageHandler(new WebSocketClient.MessageHandler() {
            @Override
            public String handleMessage(String message) {
                System.out.println("RETURN MSG FROM WSS : " + message);
                // Pass message to the controller thread.
                queue.put(message);
                // Note that the return value is not necessary.
                // You can take it out of the interface as well.
                return null;
            }
        });
    }

    @RequestMapping(value="/add", method={RequestMethod.POST, RequestMethod.OPTIONS})
    public ResponseEntity<Object> putDataToMicroservice(@RequestBody Map<String, Object> payload, @RequestHeader(value = "authorization") String authorizationHeader) throws Exception {

        // At this point you make a WebSocket request, is that right?
        doWebSocketRequest();

        // This poll call will block the current thread
        // until the WebSocket server responds,
        // or gives up waiting after the specified timeout.
        //
        // When the WebSocket server delivers a response,
        // the WS client implementation will execute the
        // @OnMessage annotated method in a thread
        // managed by the WS client itself.
        //
        // The @OnMessage method will pass the message
        // to this thread in the queue below.

        String message = queue.poll(30, TimeUnit.SECONDS);

        if (message == null) {
            // WebSocket timeout.
        }

        return ResponseEntity.ok("worked");
    }
}

Java Websocket / MessageHandler return 到全局范围？

Java Websocket / MessageHandler return to global scope?

java

websocket

message-handlers