org.opencms.gwt.client.validation.CmsValidationScheduler Maven / Gradle / Ivy
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/*
* This library is part of OpenCms -
* the Open Source Content Management System
*
* Copyright (c) Alkacon Software GmbH & Co. KG (http://www.alkacon.com)
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* For further information about Alkacon Software, please see the
* company website: http://www.alkacon.com
*
* For further information about OpenCms, please see the
* project website: http://www.opencms.org
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
package org.opencms.gwt.client.validation;
import java.util.LinkedList;
/**
* This is a helper class for scheduling form validations.
*
* Since validations can be asynchronous, it would be possible for a validation to start while another one
* is still waiting for a response from the server if it were ran directly. This might result in an inconsistent state
* of the form fields being validated. To prevent this, validation controllers use this class to schedule validations,
* and call this class again after they're finished to execute the next validation.
*
* The result of this is that a validation will only start after all unfinished validations which have been scheduled
* before it have finished running.
*
* @since 8.0.0
*/
public class CmsValidationScheduler {
/** The singleton instance of this class. */
private static CmsValidationScheduler instance = new CmsValidationScheduler();
/** The queue of validations which still need to be run. */
private LinkedList m_actions = new LinkedList();
/** A flag which indicates whether there is no validation currently running. */
private boolean m_idle = true;
/**
* Hidden default constructor.
*/
protected CmsValidationScheduler() {
// do nothing
}
/**
* Returns the singleton instance of the validation scheduler.
*
* @return the validation scheduler
*/
public static CmsValidationScheduler get() {
return instance;
}
/**
* This method should be called by the validation controller when it has finished running.
*
* It will execute the next validation if there is one.
*/
public void executeNext() {
if (!m_idle) {
if (m_actions.isEmpty()) {
m_idle = true;
} else {
CmsValidationController action = m_actions.removeFirst();
action.internalStartValidation();
}
} else {
assert false; // this shouldn't happen
}
}
/**
* This schedules a new validation to be run after all currently scheduled or running validations have finished.
*
* If there are no validations running, the validation will be started immediately.
*
* @param action the validation to be scheduled
*/
public void schedule(CmsValidationController action) {
if (m_idle) {
m_idle = false;
action.internalStartValidation();
} else {
m_actions.add(action);
}
}
}