WebSocket @OnMessage的作用

WebSocket @OnMessage的作用是在WebSocket连接上接收来自客户端发送的消息。它是一个注解，表示该方法将在WebSocket连接上接收到消息时被调用。该注解需要指定一个参数类型，该参数将包含客户端发送的消息。通常，@OnMessage方法将解析和处理客户端发送的消息，并向客户端发送响应。

相关问题

WebSocket @OnMessage

The @OnMessage annotation is used in WebSocket programming to indicate that a method in a class should be invoked when a message is received from the client.

Syntax:

@OnMessage
public void methodName(Session session, String message) {
    // code to handle received message
}

Here, the method marked with @OnMessage takes two parameters: the WebSocket session object and the message received from the client. The method body can contain any logic to process the message.

For example, the following code snippet shows how to implement a WebSocket endpoint that echoes back any messages it receives from the client:

import javax.websocket.*;
import javax.websocket.server.ServerEndpoint;

@ServerEndpoint(value = "/echo")
public class EchoEndpoint {

    @OnMessage
    public void onMessage(Session session, String message) throws Exception {
        session.getBasicRemote().sendText(message);
    }
}

In this example, the WebSocket endpoint is mapped to the "/echo" URI. The onMessage() method simply sends back the received message to the client using the session's getBasicRemote() method.

Note that the @OnMessage annotation can also be used with other data types besides String, such as ByteBuffer, InputStream, and Reader.

websocket @OnMessage有几个参数

@OnMessage注解用于标记一个方法作为WebSocket的消息处理方法。它可以有一个或两个参数，具体取决于你使用的WebSocket协议版本。

对于WebSocket协议版本为1.0的情况下，@OnMessage方法只能有一个参数，即接收到的消息内容。示例代码如下：

@OnMessage
public void onMessage(String message) {
    // 处理接收到的消息
}

对于WebSocket协议版本为2.0及以上的情况下，@OnMessage方法可以有两个参数，分别是接收到的消息内容和一个Session对象。示例代码如下：

@OnMessage
public void onMessage(String message, Session session) {
    // 处理接收到的消息，并可以使用session对象进行一些操作
}

需要注意的是，Session对象是WebSocket会话的表示，可以用于发送消息、获取会话ID等操作。