java中用websocket实现及时通讯的代码

下面是一个简单的示例代码，演示如何在Java中使用WebSocket实现即时通讯：

1. WebSocket服务器端代码：

import javax.websocket.*;
import javax.websocket.server.ServerEndpoint;
import java.io.IOException;

@ServerEndpoint("/websocket")
public class WebSocketServer {

    @OnOpen
    public void onOpen(Session session) {
        System.out.println("WebSocket connection opened: " + session.getId());
    }

    @OnMessage
    public void onMessage(String message, Session session) throws IOException {
        System.out.println("Received message from client: " + message);
        session.getBasicRemote().sendText("Server received: " + message);
    }

    @OnClose
    public void onClose(Session session, CloseReason closeReason) {
        System.out.println("WebSocket connection closed: " + session.getId() + ", Reason: " + closeReason.getReasonPhrase());
    }

    @OnError
    public void onError(Session session, Throwable throwable) {
        System.out.println("WebSocket error occurred: " + throwable.getMessage());
    }
}

2. WebSocket客户端代码：

import javax.websocket.*;
import java.net.URI;
import java.util.concurrent.CountDownLatch;

@ClientEndpoint
public class WebSocketClient {

    private static CountDownLatch latch;

    @OnOpen
    public void onOpen(Session session) {
        System.out.println("WebSocket connection opened: " + session.getId());
        try {
            session.getBasicRemote().sendText("Hello from client");
        } catch (Exception ex) {
            ex.printStackTrace();
        }
    }

    @OnMessage
    public void onMessage(String message, Session session) {
        System.out.println("Received message from server: " + message);
        latch.countDown();
    }

    @OnClose
    public void onClose(Session session, CloseReason closeReason) {
        System.out.println("WebSocket connection closed: " + session.getId() + ", Reason: " + closeReason.getReasonPhrase());
        latch.countDown();
    }

    @OnError
    public void onError(Session session, Throwable throwable) {
        System.out.println("WebSocket error occurred: " + throwable.getMessage());
        latch.countDown();
    }

    public static void main(String[] args) throws Exception {
        latch = new CountDownLatch(1);
        WebSocketContainer container = ContainerProvider.getWebSocketContainer();
        Session session = container.connectToServer(WebSocketClient.class, new URI("ws://localhost:8080/websocket"));
        latch.await();
        session.close();
    }
}

这个示例代码中，WebSocket服务器端通过`@ServerEndpoint`注解指定了WebSocket的端点URL为`/websocket`。当有客户端连接、发送消息、关闭连接或出现错误时，相应的回调方法会被触发。WebSocket客户端使用`ContainerProvider.getWebSocketContainer()`获取WebSocketContainer实例，并通过`connectToServer()`方法连接到服务器端。

请注意，这只是一个简单的示例，您可以根据自己的需求进行修改和扩展。另外，您需要确保在部署服务器时配置正确的WebSocket容器和URL。