SpringBoot环境下服务端向客户端主动推送数据的几种常见方式

@RestController
public class LongPollingController {

    private String latestData = "No new data";

    @GetMapping("/poll")
    public String poll(@RequestParam String clientId) throws InterruptedException {
        synchronized (this) {
            wait(10000); // 模拟等待新数据
        }
        return latestData;
    }

    @PostMapping("/update")
    public void updateData(@RequestBody Map<String, String> payload) {
        this.latestData = payload.get("data");
        synchronized (this) {
            notifyAll(); // 通知所有等待线程
        }
    }
}

function startPolling() {
  fetch("/poll?clientId=1")
    .then((res) => res.text())
    .then((data) => {
      console.log("Received:", data)
      startPolling() // 继续下一次轮询
    })
}

startPolling()

@RestController
public class SseController {

    private final List<SseEmitter> emitters = new CopyOnWriteArrayList<>();

    @GetMapping("/subscribe")
    public SseEmitter subscribe() {
        SseEmitter emitter = new SseEmitter(60_000L); // 超时时间
        emitters.add(emitter);
        emitter.onCompletion(() -> emitters.remove(emitter));
        return emitter;
    }

    @PostMapping("/send")
    public void sendData(@RequestBody Map<String, String> payload) {
        String message = payload.get("message");
        emitters.forEach(emitter -> {
            try {
                emitter.send(message);
            } catch (IOException e) {
                emitter.complete();
                emitters.remove(emitter);
            }
        });
    }
}

<script>
  const eventSource = new EventSource("/subscribe")

  eventSource.onmessage = function (event) {
    console.log("New message:", event.data)
  }

  eventSource.onerror = function (err) {
    console.error("EventSource failed:", err)
  }
</script>

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

@Configuration
@EnableWebSocketMessageBroker
public class WebSocketConfig implements WebSocketMessageBrokerConfigurer {

    @Override
    public void registerStompEndpoints(StompEndpointRegistry registry) {
        registry.addEndpoint("/ws").withSockJS();
    }

    @Override
    public void configureMessageBroker(MessageBrokerRegistry registry) {
        registry.enableSimpleBroker("/topic");
        registry.setApplicationDestinationPrefixes("/app");
    }
}

@Controller
public class WsController {

    @Autowired
    private SimpMessagingTemplate messagingTemplate;

    @PostMapping("/broadcast")
    public void broadcast(@RequestBody Map<String, String> payload) {
        String message = payload.get("message");
        messagingTemplate.convertAndSend("/topic/messages", message);
    }
}

<script src="https://cdn.jsdelivr.net/npm/sockjs-client@1/dist/sockjs.min.js"></script>
<script src="https://cdn.jsdelivr.net/npm/stompjs/lib/stomp.min.js"></script>

<script>
  const socket = new SockJS("/ws")
  const stompClient = Stomp.over(socket)

  stompClient.connect({}, () => {
    stompClient.subscribe("/topic/messages", (msg) => {
      console.log("Received:", msg.body)
    })
  })
</script>