JDeferred

JDeferred is a Java Deferred/Promise library similar to JQuery's Deferred Object.

Inspired by JQuery and Android Deferred Object.

Features

Deferred object and Promise
Promise callbacks
- .then(…)
- .done(…)
- .fail(…)
- .progress(…)
- .always(…)
Multiple promises
- .when(p1, p2, p3, …).then(…)
Callable and Runnable wrappers
- .when(new Runnable() {…})
Uses Executor Service
Java Generics support
- Deferred<Integer, Exception, Double> deferred;
- deferred.resolve(10);
- deferred.reject(new Exception());
- deferred.progress(0.80);
Yes, it's on Maven central repo!

Maven

<dependency>
    <groupId>org.jdeferred</groupId>
    <artifactId>jdeferred-core</artifactId>
    <version>1.0.0</version>
</dependency>

Quick Examples

Deferred object and Promise

Deferred deferred = new DeferredObject();
Promise promise = deferred.promise();
promise.done(new DoneCallback() {
  public void onDone(Object result) {
    ...
  }
}).fail(new FailCallback() {
  public void onFail(Object rejection) {
    ...
  }
}).progress(new ProgressCallback() {
  public void onProgress(Object progress) {
    ...
  }
}).always(new AlwaysCallback() {
  public void onAlways(State state, Object result, Object rejection) {
    ...
  }
});

With the reference to deferred object, you can then trigger actions/updates:

deferred.resolve("done");
deferred.reject("oops");
deferred.progress("100%");

Filter/Pipe

Deferred d = …;
Promise p = d.promise();
Promise filtered = p.then(new DoneFilter<Integer, Integer>(){
  public Integer filterDone(Integer result) P
    return result * 10;
  }
});

filtered.done(new DoneCallback<Integer>{
  public void onDone(Integer result) {
    // result would be original * 10
    System.out.println(result);
  }
});

d.resolve(3) -> 30.

Deferred Manager

DeferredManager dm = new DefaultDeferredManager();
Promise p1, p2, p3;
// initialize p1, p2, p3
dm.when(p1, p2, p3)
  .done(…)
  .fail(…)

You can also specify a Executor Service for your need.

DeferredManager dm = new DefaultDeferredManager(myExecutorService);

Runnable and Callable

You can use Callable and Runnable almost like a Promise without any additional work.

DeferredManager dm = new DefaultDeferredManager();
dm.when(new Callable<Integer>(){
  public Integer call() {
    // return something
    // or throw a new exception
  }
}).done(new DoneCallback<Integer>() {
  public void onDone(Integer result) {
    ...
  }
}).fail(new FailCallback<Throwable>() {
  public void onFail(Throwable e) {
    ...
  }
});

If you need to notify progress within your Callable or Runnable, you either need to create your own Deferred object and Promise, or you can use DeferredCallable and DeferredRunnable.

Use your own Deferred object

final Deferred deferred = ...
Promise promise = deferred.promise();
promise.then(…);
Runnable r = new Runnable() {
  public void run() {
    while (…) {
      deferred.notify(myProgress);
    }
    deferred.resolve("done");
  }
}

Or, extending DeferredRunnable

DeferredManager dm = …;
dm.when(new DeferredRunnable<Double>(){
  public void run() {
    while (…) {
      notify(myProgress);
    }
  }
}).then(…);