Java example source code file (PromiseAggregator.java)

This example Java source code file (PromiseAggregator.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

deprecated, genericfuturelistener, linkedhashset, nullpointerexception, override, promise, promiseaggregator, safevarargs, throwable, util

The PromiseAggregator.java Java example source code

/*
 * Copyright 2014 The Netty Project
 *
 * The Netty Project licenses this file to you 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 io.netty.util.concurrent;

import java.util.LinkedHashSet;
import java.util.Set;

/**
 * @deprecated Use {@link PromiseCombiner}
 *
 * {@link GenericFutureListener} implementation which consolidates multiple {@link Future}s
 * into one, by listening to individual {@link Future}s and producing an aggregated result
 * (success/failure) when all {@link Future}s have completed.
 *
 * @param <V> the type of value returned by the {@link Future}
 * @param <F> the type of {@link Future}
 */
@Deprecated
public class PromiseAggregator<V, F extends Future implements GenericFutureListener {

    private final Promise<?> aggregatePromise;
    private final boolean failPending;
    private Set<Promise pendingPromises;

    /**
     * Creates a new instance.
     *
     * @param aggregatePromise  the {@link Promise} to notify
     * @param failPending  {@code true} to fail pending promises, false to leave them unaffected
     */
    public PromiseAggregator(Promise<Void> aggregatePromise, boolean failPending) {
        if (aggregatePromise == null) {
            throw new NullPointerException("aggregatePromise");
        }
        this.aggregatePromise = aggregatePromise;
        this.failPending = failPending;
    }

    /**
     * See {@link PromiseAggregator#PromiseAggregator(Promise, boolean)}.
     * Defaults {@code failPending} to true.
     */
    public PromiseAggregator(Promise<Void> aggregatePromise) {
        this(aggregatePromise, true);
    }

    /**
     * Add the given {@link Promise}s to the aggregator.
     */
    @SafeVarargs
    public final PromiseAggregator<V, F> add(Promise... promises) {
        if (promises == null) {
            throw new NullPointerException("promises");
        }
        if (promises.length == 0) {
            return this;
        }
        synchronized (this) {
            if (pendingPromises == null) {
                int size;
                if (promises.length > 1) {
                    size = promises.length;
                } else {
                    size = 2;
                }
                pendingPromises = new LinkedHashSet<Promise(size);
            }
            for (Promise<V> p : promises) {
                if (p == null) {
                    continue;
                }
                pendingPromises.add(p);
                p.addListener(this);
            }
        }
        return this;
    }

    @Override
    public synchronized void operationComplete(F future) throws Exception {
        if (pendingPromises == null) {
            aggregatePromise.setSuccess(null);
        } else {
            pendingPromises.remove(future);
            if (!future.isSuccess()) {
                Throwable cause = future.cause();
                aggregatePromise.setFailure(cause);
                if (failPending) {
                    for (Promise<V> pendingFuture : pendingPromises) {
                        pendingFuture.setFailure(cause);
                    }
                }
            } else {
                if (pendingPromises.isEmpty()) {
                    aggregatePromise.setSuccess(null);
                }
            }
        }
    }

}