org.springframework.util.concurrent.ListenableFutureCallbackRegistry Maven / Gradle / Ivy
/*
* Copyright 2002-2013 the original author or authors.
*
* 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.
*/
package org.springframework.util.concurrent;
import java.util.LinkedList;
import java.util.Queue;
import org.springframework.util.Assert;
/**
* Registry for {@link ListenableFutureCallback} instances.
*
* Inspired by {@code com.google.common.util.concurrent.ExecutionList}.
*
* @author Arjen Poutsma
* @since 4.0
*/
public class ListenableFutureCallbackRegistry {
private final Queue> callbacks =
new LinkedList>();
private State state = State.NEW;
private Object result = null;
private final Object mutex = new Object();
/**
* Adds the given callback to this registry.
* @param callback the callback to add
*/
@SuppressWarnings("unchecked")
public void addCallback(ListenableFutureCallback callback) {
Assert.notNull(callback, "'callback' must not be null");
synchronized (mutex) {
switch (state) {
case NEW:
callbacks.add(callback);
break;
case SUCCESS:
callback.onSuccess((T)result);
break;
case FAILURE:
callback.onFailure((Throwable) result);
break;
}
}
}
/**
* Triggers a {@link ListenableFutureCallback#onSuccess(Object)} call on all added
* callbacks with the given result
* @param result the result to trigger the callbacks with
*/
public void success(T result) {
synchronized (mutex) {
state = State.SUCCESS;
this.result = result;
while (!callbacks.isEmpty()) {
callbacks.poll().onSuccess(result);
}
}
}
/**
* Triggers a {@link ListenableFutureCallback#onFailure(Throwable)} call on all added
* callbacks with the given {@code Throwable}.
* @param t the exception to trigger the callbacks with
*/
public void failure(Throwable t) {
synchronized (mutex) {
state = State.FAILURE;
this.result = t;
while (!callbacks.isEmpty()) {
callbacks.poll().onFailure(t);
}
}
}
private enum State {NEW, SUCCESS, FAILURE}
}