Java 개발: 실시간 통신을 위해 WebSocket을 사용하는 방법

<dependencies>
  <dependency>
    <groupId>javax.websocket</groupId>
    <artifactId>javax.websocket-api</artifactId>
    <version>1.1</version>
  </dependency>
  <dependency>
    <groupId>org.glassfish.tyrus</groupId>
    <artifactId>tyrus-container-grizzly-client</artifactId>
    <version>1.13</version>
  </dependency>
  <dependency>
    <groupId>javax.json</groupId>
    <artifactId>javax.json-api</artifactId>
    <version>1.1</version>
  </dependency>
  <dependency>
    <groupId>org.glassfish</groupId>
    <artifactId>javax.json</artifactId>
    <version>1.1</version>
  </dependency>
</dependencies>

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

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

    @OnOpen
    public void onOpen(Session session) {
        // 当有客户端连接时触发
        System.out.println("WebSocket连接已建立");
    }

    @OnMessage
    public String onMessage(String message, Session session) {
        // 当收到客户端消息时触发，并向客户端发送消息
        System.out.println("收到客户端消息：" + message);
        return "服务器返回消息：" + message;
    }

    @OnClose
    public void onClose(Session session, CloseReason closeReason) {
        // 当客户端断开连接时触发
        System.out.println("WebSocket连接已关闭");
    }

    @OnError
    public void onError(Throwable error) {
        // 当发生错误时触发
        System.out.println("WebSocket错误：" + error.getMessage());
    }
}

import javax.websocket.*;
import java.net.URI;

@ClientEndpoint
public class WebSocketClient {

    private Session session;
    private CountDownLatch latch;

    public WebSocketClient() {
        latch = new CountDownLatch(1);
    }

    @OnOpen
    public void onOpen(Session session) {
        // 当连接建立时触发
        System.out.println("WebSocket连接已建立");
        this.session = session;
        latch.countDown();
    }

    public void sendMessage(String message) {
        // 向服务器发送消息
        session.getAsyncRemote().sendText(message);
    }

    @OnMessage
    public void onMessage(String message) {
        // 当收到服务器消息时触发
        System.out.println("收到服务器消息：" + message);
    }

    @OnClose
    public void onClose(Session session, CloseReason closeReason) {
        // 当服务器断开连接时触发
        System.out.println("WebSocket连接已关闭");
    }
    
    @OnError
    public void onError(Throwable error) {
        // 当发生错误时触发
        System.out.println("WebSocket错误：" + error.getMessage());
    }
    
    public void close() throws InterruptedException {
        // 关闭WebSocket连接
        session.close();
        latch.await();
    }
}