Spring MVC how to get progress of running async task

I would like to start an asynchronous task from within controller like in following code sniplet from Spring docs.

import org.springframework.core.task.TaskExecutor; 

public class TaskExecutorExample { 

  private class MessagePrinterTask implements Runnable { 

    private int cn; 

    public MessagePrinterTask() { 

    } 

    public void run() { 
//dummy code 
for (int i = 0; i < 10; i++) { 
cn = i; 
} 
} 

} 

private TaskExecutor taskExecutor; 

public TaskExecutorExample(TaskExecutor taskExecutor) { 
    this.taskExecutor = taskExecutor; 
  } 

  public void printMessages() { 

      taskExecutor.execute(new MessagePrinterTask()); 

  } 
} 

afterwards in annother request (in the case that task is running) I need to check the progress of the task. Basicaly get the value of cn.

What would be the best aproach in Spring MVC a how to avoid syncronisation issues.

Thanks

Pepa Procházka