async-completable-future.md

AsyncCompletableFuture

Circumstance

• You are using the Async Context.
• There are asynchronous continuations based on a CompletableFuture instance.

Using

The AsyncCompletableFuture class repeats java.util.concurrent.CompletableFuture functionality but allows to specify the default executor. If the default executor is not defined the Asynchronizer.commonPool() is used.

The AsyncCompletableFuture class allows to set executors that honor the async context in continuations for which an executor is not defined explicitly i.e. like CompletableFuture.thenAcceptAsync(Consumer). In such cases CompletableFuture uses the ForkJoinPool.commonPool(), and it can provoke unexpected behaviour for the side that provides the future instance. At least, the async context will not be available for continuations, because they are created with the executor which does not copy the context.

IAsyncContext context = Asynchronizer.context();
context.setProperty("userId", 123);
...

AsyncCompletableFuture.completedFuture("Hello, ")
        // This continuation will have the same context
        .thenAcceptAsync(result -> {
            var userId = context.getProperty("userId");
            System.out.println(result + userId); // Output: "Hello, 123"
        })
        .get();