原文链接：https://www.dubby.cn/detail.html?id=9102

实现代码

依赖

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-websocket</artifactId>
</dependency>

启动类

@SpringBootApplication
public class Application {

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }
}

配置

@Configuration
public class WebSocketConfig implements WebSocketMessageBrokerConfigurer {
    @Bean
    public ServerEndpointExporter serverEndpointExporter (){
        return new ServerEndpointExporter();
    }
}

WebSocket

@ServerEndpoint("/websocket")
@Component
public class MyWebSocket {
    private static AtomicLong onlineCount = new AtomicLong();
    private static ConcurrentHashMap<String, Session> webSocketMap = new ConcurrentHashMap<>();
    @OnOpen
    public void onOpen(Session session) {
        webSocketMap.put(session.getId(), session);
        System.out.println("有新链接加入!当前在线人数为:\t" + onlineCount.incrementAndGet());
    }
    @OnClose
    public void onClose(Session session) {
        webSocketMap.remove(session.getId());
        System.out.println("有一链接关闭!当前在线人数为:\t" + onlineCount.decrementAndGet());
    }
    @OnMessage
    public void onMessage(String message, Session session) throws IOException {
        System.out.println("收到消息:\t" + message);
        if (message.contains("#")) {
            String[] msgMap = message.split("#");
            String targetId = msgMap[0];
            String msg = String.format("[%s]:\t%s", session.getId(), msgMap[1]);
            session.getBasicRemote().sendText(message + "[self]");
            // 单发消息
            for (Session item : webSocketMap.values()) {
                if (item.getId().equals(targetId)) {
                    sendMessage(item, msg);
                }
            }
        } else {
            String msg = String.format("[%s]:\t%s", session.getId(), message);
            session.getBasicRemote().sendText(msg + "[自己]");
            // 群发消息
            for (Session item : webSocketMap.values()) {
                if (!item.getId().equals(session.getId())) {
                    sendMessage(item, msg);
                }
            }
        }
    }
    private void sendMessage(Session session, String message) throws IOException {
        session.getBasicRemote().sendText(message);
    }
}