org.solovyev.tasks.ListenersAwareFutureTask.java Source code

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Here is the source code for org.solovyev.tasks.ListenersAwareFutureTask.java

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/*
 * Copyright 2013 serso aka se.solovyev
 *
 * 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.
 *
 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 * Contact details
 *
 * Email: se.solovyev@gmail.com
 * Site:  http://se.solovyev.org/java/jcl
 */

package org.solovyev.tasks;

import com.google.common.util.concurrent.FutureCallback;
import com.google.common.util.concurrent.Futures;
import com.google.common.util.concurrent.ListenableFutureTask;

import javax.annotation.Nonnull;
import javax.annotation.concurrent.GuardedBy;
import java.util.HashSet;
import java.util.Set;

/**
 * User: serso
 * Date: 4/9/13
 * Time: 1:12 AM
 */
final class ListenersAwareFutureTask<T> {

    @GuardedBy("listeners")
    @Nonnull
    private final Set<FutureCallback<T>> listeners = new HashSet<FutureCallback<T>>();

    @Nonnull
    private final ListenableFutureTask<T> futureTask;

    @GuardedBy("listeners")
    private volatile boolean executed = false;

    private ListenersAwareFutureTask(@Nonnull ListenableFutureTask<T> futureTask) {
        this.futureTask = futureTask;
        Futures.addCallback(futureTask, new FutureCallback<T>() {
            @Override
            public void onSuccess(T result) {
                synchronized (listeners) {
                    executed = true;
                }

                for (FutureCallback<T> listener : getListenersCopy()) {
                    listener.onSuccess(result);
                }

                synchronized (listeners) {
                    listeners.clear();
                }
            }

            @Override
            public void onFailure(Throwable t) {
                synchronized (listeners) {
                    executed = true;
                }

                for (FutureCallback<T> listener : getListenersCopy()) {
                    listener.onFailure(t);
                }

                synchronized (listeners) {
                    listeners.clear();
                }
            }
        });
    }

    @Nonnull
    static <T> ListenersAwareFutureTask<T> create(@Nonnull ListenableFutureTask<T> futureTask) {
        return new ListenersAwareFutureTask<T>(futureTask);
    }

    @Nonnull
    private Set<FutureCallback<T>> getListenersCopy() {
        synchronized (listeners) {
            return new HashSet<FutureCallback<T>>(listeners);
        }
    }

    public boolean addListener(@Nonnull FutureCallback<T> listener) {
        synchronized (listeners) {
            if (!executed) {
                return listeners.add(listener);
            } else {
                // too late
                return false;
            }
        }
    }

    public boolean removeListener(@Nonnull FutureCallback<T> listener) {
        synchronized (listeners) {
            return listeners.remove(listener);
        }
    }

    public void removeAllListeners() {
        synchronized (listeners) {
            listeners.clear();
        }
    }

    @Nonnull
    public ListenableFutureTask<T> getFutureTask() {
        return futureTask;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o)
            return true;
        if (o == null || getClass() != o.getClass())
            return false;

        ListenersAwareFutureTask that = (ListenersAwareFutureTask) o;

        if (!futureTask.equals(that.futureTask))
            return false;

        return true;
    }

    @Override
    public int hashCode() {
        return futureTask.hashCode();
    }
}