java - 在创建简单websocket的程序中，在哪里调用onOpen方法？

我找到了创建简单Websocket连接的代码。
在主函数中，仅调用WebsocketClientEndpoint的构造函数，而在构造函数中看不到对onOpen函数的调用。在输出中，按照onOpen函数中的指定打印“ opening websocket”。谁能告诉我onOpen函数的调用在哪里发生？

TestApp.java：

package testapp;

import java.net.URI;
import java.net.URISyntaxException;

public class TestApp {

public static void main(String[] args) {
    try {
        // open websocket
        final WebsocketClientEndpoint clientEndPoint = new WebsocketClientEndpoint(new URI("wss://real.okcoin.cn:10440/websocket/okcoinapi"));

        // add listener
        clientEndPoint.addMessageHandler(new WebsocketClientEndpoint.MessageHandler() {
            public void handleMessage(String message) {
                System.out.println(message);
            }
        });

        // send message to websocket
        clientEndPoint.sendMessage("{'event':'addChannel','channel':'ok_btccny_ticker'}");

        // wait 5 seconds for messages from websocket
        Thread.sleep(5000);

    } catch (InterruptedException ex) {
        System.err.println("InterruptedException exception: " + ex.getMessage());
    } catch (URISyntaxException ex) {
        System.err.println("URISyntaxException exception: " + ex.getMessage());
    }
}

}

WebsocketClientEndpoint.java

package testapp;

import java.net.URI;
import javax.websocket.ClientEndpoint;
import javax.websocket.CloseReason;
import javax.websocket.ContainerProvider;
import javax.websocket.OnClose;
import javax.websocket.OnMessage;
import javax.websocket.OnOpen;
import javax.websocket.Session;
import javax.websocket.WebSocketContainer;

 /**
 * ChatServer Client
 *
 * @author Jiji_Sasidharan
 */
@ClientEndpoint
public class WebsocketClientEndpoint {

Session userSession = null;
private MessageHandler messageHandler;

public WebsocketClientEndpoint(URI endpointURI) {
    try {
        WebSocketContainer container = ContainerProvider.getWebSocketContainer();
        container.connectToServer(this, endpointURI);
    } catch (Exception e) {
        throw new RuntimeException(e);
    }
}

/**
 * Callback hook for Connection open events.
 *
 * @param userSession the userSession which is opened.
 */
@OnOpen
public void onOpen(Session userSession) {
    System.out.println("opening websocket");
    this.userSession = userSession;
}

/**
 * Callback hook for Connection close events.
 *
 * @param userSession the userSession which is getting closed.
 * @param reason the reason for connection close
 */
@OnClose
public void onClose(Session userSession, CloseReason reason) {
    System.out.println("closing websocket");
    this.userSession = null;
}

/**
 * Callback hook for Message Events. This method will be invoked when a client send a message.
 *
 * @param message The text message
 */
@OnMessage
public void onMessage(String message) {
    if (this.messageHandler != null) {
        this.messageHandler.handleMessage(message);
    }
}

/**
 * register message handler
 *
 * @param message
 */
public void addMessageHandler(MessageHandler msgHandler) {
    this.messageHandler = msgHandler;
}

/**
 * Send a message.
 *
 * @param user
 * @param message
 */
public void sendMessage(String message) {
    this.userSession.getAsyncRemote().sendText(message);
}

/**
 * Message handler.
 *
 * @author Jiji_Sasidharan
 */
public static interface MessageHandler {

    public void handleMessage(String message);
}
}

最佳答案

您必须阅读注释的工作原理才能理解这一点。@OnOpen是注释。 @OnOpen允许我们拦截新会话的创建。

注释类型OnOpen


  @Retention（值=运行时间）
  @Target（值=方法）
  公共@interface OnOpen
  
  此方法级别注释可用于装饰Java方法
  当新的Web套接字会话打开时希望被调用。
  
  该方法只能采用以下参数：
  
  可选的会话参数
    可选的EndpointConfig参数
    零到n个用PathParam注释注释的字符串参数。
  
  参数可以以任何顺序出现。