Wait for some Spring ListenableFuture

Question

There is a service which uses Spring AsyncRestTemplate for sending rest calls. Each call of AsyncRestTemplate.exchange() returns ListenableFuture. Something like this:

    ListenableFuture future1 = new AsyncRestTemplate().exchange(...);
    ListenableFuture future2 = new AsyncRestTemplate().exchange(...);
    ListenableFuture future3 = new AsyncRestTemplate().exchange(...);

Is there a way for create single ListenableFuture which combines all other calls? Something like Futures.allAsList from Guava.

Your best bet is to use an adapter like this one: [Future Converter](https://github.com/lukas-krecan/future-converter) — Nicolas Labrot, Apr 11 '17 at 12:34

Gagandeep Kalra · Answer 1 · 2018-01-27T07:26:40.970

Step #1: Convert each ListenableFuture to CompletableFuture

public CompletableFuture<T> toCompletableFuture(ListenableFuture<ResponseEntity<String>> listenableFuture) {
    final CompletableFuture<T> completableFuture = new CompletableFuture<>();

    listenableFuture.addCallback(new ListenableFutureCallback<ResponseEntity<String>>() {
        @Override
        public void onFailure(Throwable e) {
            completableFuture.completeExceptionally(e);
            }
        }

        @Override
        public void onSuccess(ResponseEntity<String> result) {
            completableFuture.complete(parseResponse(result));
            }
        }
    });
    return completableFuture;
}

Step #2: call CompletableFuture.allOf(cF1, cF2, cF3...)

in spring 5 there is org.springframework.util.concurrent.ListenableFuture#completable method which does the same thing. — destan, Aug 08 '17 at 12:47

score 3 · Answer 2 · answered Dec 16 '19 at 16:04

Since Spring 5.0, ListenableFuture implements the method completable() which does exactly what you need:

    /**
     * Expose this {@link ListenableFuture} as a JDK {@link CompletableFuture}.
     * @since 5.0
     */
    default CompletableFuture<T> completable() {

Wait for some Spring ListenableFuture

2 Answers2