Spring MVC：控制器与异步方法之间的通信

Question

What I'm trying to achieve...

From a @Controller method, get the execution status of an asynchronous process so that I can display the current progress in a HTML page.

Scenario:

1. User opens http://localhost/foo , controller instantiates the BackgroundAsyncService and calls workAsync method. The BackgroundAsyncService is autowired to controller.
2. User opens http://localhost/foo-1 and wants to see what the status of the process previously started. From JSP I'm using AJAX to poll the controller.

Questions

Is it possible to get value of i after the workAsync method was called?
What should be the topic on what I must document to so that I can arrive to an answer to the above?

Service class

@Service
public class BackgroundAsyncService implements FutureService {

  private static final Logger LOGGER = Logger.getLogger(BackgroundAsyncService.class);

  @Async
  public Future<String> workAsync() {
    LOGGER.debug("workAsync begin...");
    try {
      for (int i = 0; i <= 1000; i++) {
        Thread.sleep(100);
        LOGGER.debug("i : " + i);
      }
    } catch (InterruptedException interruptedException) {
      LOGGER.error(interruptedException);
    }
    LOGGER.debug("workAsync end.");
    return new AsyncResult<String>("foo");
  }

}

I'm using

Spring 4.2.5.RELEASE
Java 1.7

Answer 1

Your Async method could be updating a register in a DB, a Cache or just a simple final static HashMap and then your page check the value. If you want to notify the page deferred result

Have in mind that you might need a distributed cache if your application is being replicated when not using a DB.

Answer 2

Using the ApplicationContext you can get BackgroundAsyncService component from spring container. From default it is singleton so it should be the same instance. In some action which is reference to http://localhost/foo-1 you can get "i" value.

BackgroundAsyncService backgroundAsyncService = (BackgroundAsyncService) context.getBean(BackgroundAsyncService.class);
int i = backgroundAsyncService.getI();

You can try resize BackgroundAsyncService class:

@Service
public class BackgroundAsyncService implements FutureService {

    private static final Logger LOGGER = Logger.getLogger(BackgroundAsyncService.class);

    private int i;

    public int getI() {
        return i;
    }


    @Async
    public Future<String> workAsync() {
        LOGGER.debug("workAsync begin...");
        try {
            for (this.i = 0; this.i <= 1000; this.i++) {
               Thread.sleep(100);
               LOGGER.debug("i : " + this.i);
            }
        } catch (InterruptedException interruptedException) {
            LOGGER.error(interruptedException);
        }
        LOGGER.debug("workAsync end.");
        return new AsyncResult<String>("foo");
    }

}