What's the advantage of using Spring Async vs. Just returning the CompletableFuture
on your own?
There is no “vs.” between the two: these are complementary technologies:
CompletableFuture
provides a convenient way to chain different stages of asynchronous computation – with more flexibility than Spring's ListenableFuture
;@Async
provides convenient management of your background tasks and threads, with standard Spring configuration for your executor(s).But both can be combined (since Spring 4.2). Suppose you want to turn the following method into a background task returning a CompletableFuture
:
public String compute() {
// do something slow
return "my result";
}
What you have to do:
@EnableAsync
and an Executor
bean@Async
CompletableFuture.completedFuture()
@Async
public CompletableFuture<String> computeAsync() {
// do something slow - no change to this part
// note: no need to wrap your code in a lambda/method reference,
// no need to bother about executor handling
return CompletableFuture.completedFuture("my result");
}
As you notice, you don't have to bother about submitting the background task to an executor: Spring takes care of that for you. You only have to wrap the result into into a completed CompletableFuture
so that the signature matches what the caller expects.