001/*
002 * This library is part of OpenCms -
003 * the Open Source Content Management System
004 *
005 * Copyright (C) Alkacon Software (http://www.alkacon.com)
006 *
007 * This library is free software; you can redistribute it and/or
008 * modify it under the terms of the GNU Lesser General Public
009 * License as published by the Free Software Foundation; either
010 * version 2.1 of the License, or (at your option) any later version.
011 *
012 * This library is distributed in the hope that it will be useful,
013 * but WITHOUT ANY WARRANTY; without even the implied warranty of
014 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
015 * Lesser General Public License for more details.
016 *
017 * For further information about Alkacon Software, please see the
018 * company website: http://www.alkacon.com
019 *
020 * For further information about OpenCms, please see the
021 * project website: http://www.opencms.org
022 *
023 * You should have received a copy of the GNU Lesser General Public
024 * License along with this library; if not, write to the Free Software
025 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
026 */
027
028package org.opencms.gwt.client.util;
029
030import java.util.HashSet;
031import java.util.Set;
032
033/**
034 * Helper class used to perform an action when multiple asynchronous tasks have finished.<p>
035 *
036 * To use this, first, for every action, add a token which uniquely identifies the action. Remove the corresponding
037 * token when the action is finished. When all tokens are removed, the final action will be executed.<p>
038 */
039public class CmsAsyncJoinHandler {
040
041    /** The action to perform when all tokens have been removed. */
042    private Runnable m_joinAction;
043
044    /** The set of tokens. */
045    protected Set<Object> m_tokens = new HashSet<Object>();
046
047    /**
048     * Creates a new instance.<p>
049     *
050     * @param joinAction the final action to execute
051     */
052    public CmsAsyncJoinHandler(Runnable joinAction) {
053
054        m_joinAction = joinAction;
055    }
056
057    /**
058     * Adds tokens.<p>
059     *
060     * @param tokens the tokens to add
061     */
062    public void addTokens(Object... tokens) {
063
064        for (Object token : tokens) {
065            m_tokens.add(token);
066        }
067    }
068
069    /**
070     * Removes a token.<p>
071     *
072     * When all tokens have been removed, the final action is executed.<p>
073     *
074     * @param token the token to remove
075     */
076    public void removeToken(Object token) {
077
078        m_tokens.remove(token);
079        if (m_tokens.isEmpty()) {
080            if (m_joinAction != null) {
081                m_joinAction.run();
082            }
083        }
084    }
085
086}