001/*
002 * CDDL HEADER START
003 *
004 * The contents of this file are subject to the terms of the
005 * Common Development and Distribution License, Version 1.0 only
006 * (the "License").  You may not use this file except in compliance
007 * with the License.
008 *
009 * You can obtain a copy of the license at legal-notices/CDDLv1_0.txt
010 * or http://forgerock.org/license/CDDLv1.0.html.
011 * See the License for the specific language governing permissions
012 * and limitations under the License.
013 *
014 * When distributing Covered Code, include this CDDL HEADER in each
015 * file and include the License file at legal-notices/CDDLv1_0.txt.
016 * If applicable, add the following below this CDDL HEADER, with the
017 * fields enclosed by brackets "[]" replaced with your own identifying
018 * information:
019 *      Portions Copyright [yyyy] [name of copyright owner]
020 *
021 * CDDL HEADER END
022 *
023 *
024 *      Copyright 2006-2010 Sun Microsystems, Inc.
025 *      Portions Copyright 2015 ForgeRock AS.
026 */
027package org.opends.quicksetup.util;
028
029
030
031/**
032 * This class provides a mechanism for running a task in the background using a
033 * separate thread and providing the caller with notification when it has
034 * completed.
035 * @param <T> type of object returned by this process
036 */
037public abstract class BackgroundTask<T>
038{
039  /**
040   * Creates a new thread and begins running the task in the background.  When
041   * the task has completed, the {@code backgroundTaskCompleted} method will be
042   * invoked.
043   */
044  public final void startBackgroundTask()
045  {
046    BackgroundTaskThread<T> taskThread = new BackgroundTaskThread<>(this);
047    taskThread.start();
048  }
049
050
051
052  /**
053   * Performs all processing associated with the task.
054   *
055   * @return  An {@code Object} with information about the processing performed
056   *          for this task, or {@code null} if no return value is needed.
057   *
058   * @throws Throwable throwable that will be passed through the method
059   *          backgroundTaskCompleted.
060   */
061  public abstract T processBackgroundTask() throws Throwable;
062
063
064
065  /**
066   * This method will be invoked to indicate that the background task has
067   * completed.  If processing completed successfully, then the
068   * {@code Throwable} argument will be {@code null} and the {@code returnValue}
069   * argument will contain the value returned by the
070   * {@code processBackgroundTask} method.  If an exception or error was thrown,
071   * then the {@code throwable} argument will not be {@code null}.
072   *
073   * @param  returnValue  The value returned by the
074   *                      {@code processBackgroundTask} method when processing
075   *                      completed, or {@code null} if no value was returned or
076   *                      an exception was encountered during processing.
077   * @param  throwable    A {@code Throwable} instance (e.g., an exception) that
078   *                      was raised during processing, or {@code null} if all
079   *                      processing completed successfully.
080   */
081  public abstract void backgroundTaskCompleted(T returnValue,
082                                               Throwable throwable);
083}