Spring使用DeferredResult实现长连接

@RestController
@RequestMapping("/notifications")
public class NotificationResource implements ReleaseMessageListener {
    private static final Logger logger = LoggerFactory.getLogger(NotificationResource.class);

    private final Multimap deferredResults =
            Multimaps.synchronizedSetMultimap(HashMultimap.create());
    // 线程池
    private final ExecutorService largeNotificationBatchExecutorService;


    public NotificationResource() {
        largeNotificationBatchExecutorService = Executors.newFixedThreadPool(20, BambooThreadFactory.create
                ("NotificationResource", true));
    }

    /**
     * 接收所有实例链接
     * @return
     */
    @RequestMapping(method = RequestMethod.GET)
    public DeferredResult> pollNotification(@RequestParam(value = "instanceId") String instanceId) {
        DeferredResultWrapper deferredResultWrapper = new DeferredResultWrapper(instanceId);
        deferredResultWrapper.onTimeout(() -> logger.debug("notifications timeout"));
        deferredResultWrapper.onCompletion(() -> deferredResults.remove("server", deferredResultWrapper));
        this.deferredResults.put("server", deferredResultWrapper);

        return deferredResultWrapper.getResult();
    }


    /**
     * 通知所有实例
     */
    @Override
    public void handleMessage() {
        logger.info("gray map modified");
        for (DeferredResultWrapper wrapper : (List) new ArrayList(deferredResults.get("server"))) {
            largeNotificationBatchExecutorService.submit(() -> wrapper.setResult(true));
        }

    }
}

通知接口

/**
 * 通知接口
 */
public interface ReleaseMessageListener {
    void handleMessage();
}

deferredResult包装类

/**
 * 长链接包装类
 */
public class DeferredResultWrapper {
    private static final long TIMEOUT = 60 * 1000;//60 seconds
    // 默认返回304
    private static final ResponseEntity
            NOT_MODIFIED_RESPONSE = new ResponseEntity<>(HttpStatus.NOT_MODIFIED);
    private String instanceId;
    private DeferredResult> result;

    /**
     * 构造函数
     */
    public DeferredResultWrapper(String instanceId) {
        this.instanceId = instanceId;
        result = new DeferredResult<>(TIMEOUT, NOT_MODIFIED_RESPONSE);
    }

    // 超时
    public void onTimeout(Runnable timeoutCallback) {
        result.onTimeout(timeoutCallback);
    }

    public void onCompletion(Runnable completionCallback) {
        result.onCompletion(completionCallback);
    }

    /**
     * 设置返回结果
     * @param notification
     */
    public void setResult(boolean notification) {
        result.setResult(new ResponseEntity<>(notification, HttpStatus.OK));
    }

    public DeferredResult> getResult() {
        return result;
    }
}

当调用接口时，都会在本地注册。

当到达60s超时时间后，会返回给调用方304。

当在60s之内想要通知调用方，会返回true且200。