springboot 长轮询实现

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springboot 长轮询实现

基于 @EnableAsync , @Sync

@SpringBootApplication
@EnableAsync
public class DemoApplication {
	public static void main(String[] args) {
		SpringApplication.run(DemoApplication.class, args);
	}
}

@RequestMapping("/async")
@RestController
public class AsyncRequestDemo {

    @Autowired
    private AsyncRequestService asyncRequestService;

    @GetMapping("/value")
    public String getValue() {

        String msg =  null;
        Future<String> result = null;
        try{
            result = asyncRequestService.getValue();
            msg = result.get(10, TimeUnit.SECONDS);
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            if (result != null){
                result.cancel(true);
            }
        }

        return msg;
    }

    @PostMapping("/value")
    public void postValue(String msg) {
        asyncRequestService.postValue(msg);
    }
}

@Service
public class AsyncRequestService {

    private String msg = null;

    @Async
    public Future<String> getValue() throws InterruptedException {

        while (true){
            synchronized (this){
                if (msg != null){
                    String resultMsg = msg;
                    msg = null;
                    return new AsyncResult(resultMsg);
                }
            }
            Thread.sleep(100);
        }
    }

    public synchronized void postValue(String msg) {
        this.msg = msg;
    }
}

备注

1. @EnableAsync 开启异步
2. @Sync 标记异步方法
3. Future 用于接收异步返回值
4. result.get(10, TimeUnit.SECONDS); 阻塞，超时获取结果
5. Future.cancel() 中断线程