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The AWS SDK for Java with support for OSGi. The AWS SDK for Java provides Java APIs for building software on AWS' cost-effective, scalable, and reliable infrastructure products. The AWS Java SDK allows developers to code against APIs for all of Amazon's infrastructure web services (Amazon S3, Amazon EC2, Amazon SQS, Amazon Relational Database Service, Amazon AutoScaling, etc).

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/*
 * Copyright 2013-2016 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License").
 * You may not use this file except in compliance with the License.
 * A copy of the License is located at
 *
 *  http://aws.amazon.com/apache2.0
 *
 * or in the "license" file accompanying this file. This file 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 com.amazonaws.services.s3.transfer.internal;

import com.amazonaws.event.DeliveryMode;
import com.amazonaws.event.ProgressListener;
import com.amazonaws.event.SDKProgressPublisher;
import com.amazonaws.services.s3.transfer.PersistableTransfer;

import org.apache.commons.logging.LogFactory;

import java.util.concurrent.Future;

/**
 * Used to publish transfer events.
 */
public class S3ProgressPublisher extends SDKProgressPublisher {
    /**
     * Used to deliver a persistable transfer to the given s3 listener.
     *
     * @param listener only listener of type {@link S3ProgressListener} will be
     * notified.
     *
     * @return the future of a submitted task; or null if the delivery is
     * synchronous with no future task involved.  Note a listener should never
     * block, and therefore returning null is the typical case.
     */
    public static Future publishTransferPersistable(
            final ProgressListener listener,
            final PersistableTransfer persistableTransfer) {
        if (persistableTransfer == null || !(listener instanceof S3ProgressListener)) {
            return null;
        }
        final S3ProgressListener s3listener = (S3ProgressListener)listener;
        return deliverEvent(s3listener, persistableTransfer);
    }

    private static Future deliverEvent(final S3ProgressListener listener,
            final PersistableTransfer persistableTransfer) {
        if (listener instanceof DeliveryMode) {
            DeliveryMode mode = (DeliveryMode) listener;
            if (mode.isSyncCallSafe()) {
                // Safe to call the listener directly
                return quietlyCallListener(listener, persistableTransfer);
            }
        }

        // Not safe to call the listener directly; so submit an async task.
        // This is unfortunate as the listener should never block in the first
        // place, but such task submission is necessary to remain backward
        // compatible.
        return setLatestFutureTask(getExecutorService().submit(new Runnable() {
            @Override public void run() {
                listener.onPersistableTransfer(persistableTransfer);
            }
        }));
    }

    private static Future quietlyCallListener(
            final S3ProgressListener listener,
            final PersistableTransfer persistableTransfer) {
        try {
            listener.onPersistableTransfer(persistableTransfer);
        } catch(Throwable t) {
            // That's right, we need to suppress all errors so as to be on par
            // with the async mode where all failures will be ignored.
            LogFactory.getLog(S3ProgressPublisher.class)
                .debug("Failure from the event listener", t);
        }
        return null;
    }
}