Java returning before tasks complete

Question

I have a method and it calls another method, for which the result is not important. To be exact, it is a POST request to a web service and the result is processed in that method and not in the calling method. Now I want the main method to return before that task finishes.

In essence, I need some sort of asynchronousity. What tools can I use in Java? Here are the steps again:

Method A calls Method B
Method B starts executing (we are not interested in the results of method b: it makes a call to a web service and processes the results itself)
Method A returns before Method B finishes

Add a callback in method B that runs once it has completed – nbokmans Dec 24 '15 at 08:28 — nbokmans, Dec 24 '15 at 08:28

score 2 · Answer 1 · answered Dec 24 '15 at 08:30

2

You can use CompletableFuture.runAsync() to call method B async.

You can add a callback by calling .thenRun() on returned future if you want to do something when method B exited

answered Dec 24 '15 at 08:30

Prim

2,880
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Jay · Accepted Answer · 2015-12-24T09:09:10.940

1

If you are using Spring then its very easy and without any boilerplate code. Have a look at @Async support in Spring. Here is a very simple example to get you quickly started.

@Service
public class YourClass {
    public void methodA() {
        methodB();
    }

    @Async
    public void methodB() {
        // Your POST logic
    }
}

To enable async support in your xml configuration, you need to have something like below

<task:annotation-driven />
<task:executor id="defaultAsyncTaskExecutor" pool-size="5-15" queue-capacity="100" />

edited Dec 24 '15 at 09:09

answered Dec 24 '15 at 08:49

Jay

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Hi Jay, I am indeed using Spring and this is the solution I am currently leaning towards. Just looking at how to set up my xml config for this solution. Do you have any advice on that? – Kevin Wu Dec 24 '15 at 09:01
Updated the answer to have xml configuration – Jay Dec 24 '15 at 09:05
What if methodA() has a return value such as String. Will this still work the same? I am working through a similar issue and I haven't been able to get method A to return before method B completes. – Jim Stevens Jul 12 '20 at 16:56
@JimStevens yes it will just work the same as void method in above example – Jay Jul 13 '20 at 20:11
btw the [answer from Prim](https://stackoverflow.com/a/34449649/471467) is also a nice neat way to do if you are using Java 8 or later. No dependency on framework supporting async mechanism. – Jay Jul 13 '20 at 20:13

score 0 · Answer 3 · answered Dec 24 '15 at 08:31

0

new Thread(new Runnable() {
    public void run() {
        //Do whatever
    }
}).start();

answered Dec 24 '15 at 08:31

David Petran

3
1
4

please, explain your answer – ArtKorchagin Dec 24 '15 at 08:51

score 0 · Answer 4 · answered Dec 24 '15 at 08:33

Try to use AsyncHttpClient ,example

`AsyncHttpClient asyncHttpClient = new AsyncHttpClient(
                                builder.setFollowRedirect(true).
                                setWebSocketTimeout(120000).
                                setAcceptAnyCertificate(true).
                                setMaxConnections(100).
                                setMaxRequestRetry(3).
                                setReadTimeout(120000).
                                setConnectTimeout(120000).
                                setRequestTimeout(120000).
                                build()); 
asyncHttpClient.prepareGet(url).execute(new AsyncCompletionHandler<Response>(){
                                @Override
                                public Response onCompleted(Response response) throws Exception{
                                      //your logic here
                                    }

                                @Override
                                public void onThrowable(Throwable t){
                                    //your logic here
                                }
                        });

`

Java returning before tasks complete

4 Answers4