Java 通知设计模式

Question

我有一个基于网络的应用程序，每次在后端执行某些操作时，它都会从服务器向客户端发送消息。现在，我正在编写一些测试来查看发送到客户端的消息是否是预期的消息。每个操作在执行时都会生成一条发送到客户端的特定消息。在我的测试中，我创建了一个 WebSocket 客户端来监听服务器。现在，当我执行某个操作时，我应该检查是否正在发送该操作的预期消息。请注意，服务器需要一些时间来发送消息。

以下只是伪代码:

class ApplicationTest
    public void checkIfEventCreatedMsgIsSent() {
        Application.createNewEvent("Id101");
        // Wait till the application sends message to the client
        // And then check that the message sent is the correct one
        // if (expectedMessage == recievedMessageFromClient) {
        //   success();
        // }

    }

class Client
    public void readMessage(Message message) {
        // Received the new event message with Id101
        // Now this message should be sent to ApplicationTest.checkIfEventCreatedMsgIsSent and confirmed by it
    }
}

我收到消息给客户，一切都很好。

但我无法弄清楚如何通知 ApplicationTest 客户端已收到消息，然后进行验证。我尝试在这里实现观察者设计模式，但这只会让人更加困惑。我应该如何实现这个以及哪种设计模式最适合这种场景？

Answer 1

用一些基本假设重写你的类

我们正在存储一个值的映射，例如 Map<String, Object> msg = new HashMap<String, Object>()它将加载 (EventId, EventDetailsObject).上面的 Map msg 将存储在 ServletContext 中，它也可以是 MQ 上的持久消息或 db 中的值。客户端不发送任何确认，但 ApplicationTest 会轮询以查找事件是否已创建尽量不深入了解其他实现细节，请告诉我这对您是否有意义？

class ApplicationTest
    public void checkIfEventCreatedMsgIsSent() {
        Application.createNewEvent("Id101");
        // Wait till the application sends message to the client
        // And then check that the message sent is the correct one
        // if (expectedMessage == recievedMessageFromClient) {
        //   success();
        // }
        int iCount = 0;
        int final MAXCOUNT = 5;
        // Assuming client doesnt send an acknowledgement 
            // but Server pools to find that
        // Below is Polling code method to check if  event is created
        // Servlet context is an example
            // it could be a persistent message on MQ or a value in db
        while(iCount < 5) {
             if (servletcontext.get(msg).get("Id101") == null) {
                 count++;
                 sleep(5000);
             } else { System.out.println("Eureka, msg is sent!")}
        }
    }
class Client{
   public void readMessage(Message message) {
        // Received the new event message with Id101
        // Now this message should be sent to 
            // ApplicationTest.checkIfEventCreatedMsgIsSent and confirmed by it
        // Below msg is a singleton object in Servlet context as an example
            // it could be a persistent message on MQ or a value in db
        // Map<String, Object> msg = new HashMap<String, Object>();
        synchronized(servletContext) {
            servletcontext.get(msg).put("Id101", <object>);
        }
    }
}