io.joynr.provider.Promise Maven / Gradle / Ivy
package io.joynr.provider;
/*
* #%L
* %%
* Copyright (C) 2011 - 2015 BMW Car IT GmbH
* %%
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
* #L%
*/
import java.util.ArrayList;
import java.util.List;
public class Promise {
private T deferred;
private List listeners = new ArrayList();
public Promise(T deferred) {
this.deferred = deferred;
this.deferred.addListener(new DeferredListener() {
@Override
public void onSettlement() {
notifyListeners();
}
});
}
/**
* Adds a listener that is called once the promise is settled. NOTE: If the
* promise is already settled when adding the listener, the thread adding
* the listener will be used to execute the listener.
* @param listener the listener that will be called once the promise is settled
*/
public void then(PromiseListener listener) {
if (listener == null) {
return;
}
listeners.add(listener);
if (isSettled()) {
notifyListener(listener);
}
}
private void notifyListeners() {
for (PromiseListener listener : listeners) {
notifyListener(listener);
}
}
private void notifyListener(PromiseListener listener) {
if (isFulfilled()) {
listener.onFulfillment(deferred.getValues());
} else if (isRejected()) {
listener.onRejection(deferred.getError());
}
}
public boolean isFulfilled() {
return deferred.isFulfilled();
}
public boolean isRejected() {
return deferred.isRejected();
}
/**
* @return true if the promise is fulfilled or rejected; false if the
* promise is pending.
*/
public boolean isSettled() {
return deferred.isSettled();
}
}