What is wrong with @Async

[Yogesh Gandhi]

Hi,

I need to call a method asynchronously. This is what I did, by studying from internet.
Similar code is working in our project, with the same annotations and all, but due to some reason, I am not able to make it work in standalone.

Can anybody help me on this, as to what I have done wrong.

import java.util.concurrent.Future;

import org.springframework.scheduling.annotation.Async;
import org.springframework.scheduling.annotation.AsyncResult;
import org.springframework.scheduling.annotation.EnableAsync;

public class JBPMClient {

	public static void main(String[] as) throws Exception {
		Util u = new Util();
		Future<String> future = u.test();
		System.out.println("I am done");
	}
}
@EnableAsync
class Util
{
	@Async
	public Future<String> test()
	{
		System.out.println(System.currentTimeMillis()/1000 + " Entered test....");
		try {
			Thread.sleep(10000);
		} catch (InterruptedException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		System.out.println(System.currentTimeMillis()/1000 + " HELLO");
		return new AsyncResult<String>("HELLO");
		
	}
}

[Yogesh Gandhi]

THe output is

"Entered test"
Then waits for 10 seconds
"HELLO"
and then
I am done.

[Ankit Garg]

See this tutorial, you have to run your application using Spring not directly by instantiating the class

[Yogesh Gandhi]

Ankit Garg wrote:See this tutorial, you have to run your application using Spring not directly by instantiating the class

I wonder, what is it that it is only required to run my application using spring. Why I can't use it on a method in plain java?

[Paul Clapham]

If you want to use an annotation on a class like that, you have to use the class in a context (or framework) which is programmed to use the annotation. It isn't the JVM code which is going to use the annotation, it's some application code somewhere.

You know already that Spring is an example of such an application, it uses that @Async annotation in the way you expect. It would be possible for you to write an application which used that annotation in the same way, but you would actually have to write the code for that usage to happen.

[Jesper de Jong]

This is a very common mistake that people make when they use Spring: if you create an instance of a Spring bean with new, then it is not a Spring-managed bean, and things like dependency injection (@Autowired) and other Spring features (such as @Async) will not work.

You need to let Spring manage the instance of the Util class, instead of creating it yourself using new.