An alternative implementation to Java 8 CompletableFuture. Its main focus is to simplify support of CompletionStage in other libraries.
The objective is to provide a simple, easy to understand alternative. You can check the code and see for yourself.
Add Maven dependency
<dependency>
<groupId>net.javacrumbs.completion-stage</groupId>
<artifactId>completion-stage</artifactId>
<version>0.0.9</version>
</dependency>And enjoy
private final CompletionStageFactory factory =
new CompletionStageFactory(defaultAsyncExecutor);
...
CompletableCompletionStage<Object> completionStage = factory.createCompletionStage();
...
// once the result is ready, let us know
completionStage.complete(value);
...
// in case of exception
completionStage.completeExceptionally(exception);
...
// create already completed stage
CompletionStage<String> completed = factory.completedStage(value);
...
// asynchronously execute supplier
CompletionStage<String> asyncStage = factory.supplyAsync(supplier);For example, to convert Spring ListenableFuture to CompletionStage you can
CompletableCompletionStage<Object> completionStage = factory.createCompletionStage();
springListenableFuture.addCallback(new ListenableFutureCallback<String>() {
@Override
public void onSuccess(String result) {
completionStage.complete(result);
}
@Override
public void onFailure(Throwable t) {
completionStage.completeExceptionally(t);
}
});The best way to understand how it works is to check the code. I have written two articles describing design decisions behind the implementation you can read it here and here.
You definitely can. The main problem I have that it is tightly coupled with fork-join framework. And fork-join framework is meant to be used mainly for CPU intensive tasks. But my usual use-case is the opposite, I want to use asynchronous processing mainly for blocking tasks. I do not want to block a thread while waiting for a network or database operation.
Of course, you do not have to use fork-join executors with CompletableFutures. You just have to be careful since it is the default choice for async methods.