scheduler.java

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/* 
 * Copyright 2004-2005 OpenSymphony 
 * 
 * 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.
 * 
 */

/*
 * Previously Copyright (c) 2001-2004 James House
 */
package org.quartz;

import java.util.Date;
import java.util.List;
import java.util.Set;

import org.quartz.spi.JobFactory;

/**
 * <p>
 * This is the main interface of a Quartz Scheduler.
 * </p>
 * 
 * <p>
 * A <code>Scheduler</code> maintains a registery of <code>{@link org.quartz.JobDetail}</code>
 * s and <code>{@link Trigger}</code>s. Once registered, the <code>Scheduler</code>
 * is responible for executing <code>Job</code> s when their associated
 * <code>Trigger</code> s fire (when their scheduled time arrives).
 * </p>
 * 
 * <p>
 * <code>Scheduler</code> instances are produced by a <code>{@link SchedulerFactory}</code>.
 * A scheduler that has already been created/initialized can be found and used
 * through the same factory that produced it. After a <code>Scheduler</code>
 * has been created, it is in "stand-by" mode, and must have its 
 * <code>start()</code> method called before it will fire any <code>Job</code>s.
 * </p>
 * 
 * <p>
 * <code>Job</code> s are to be created by the 'client program', by defining
 * a class that implements the <code>{@link org.quartz.Job}</code>
 * interface. <code>{@link JobDetail}</code> objects are then created (also
 * by the client) to define a individual instances of the <code>Job</code>.
 * <code>JobDetail</code> instances can then be registered with the <code>Scheduler</code>
 * via the <code>scheduleJob(JobDetail, Trigger)</code> or <code>addJob(JobDetail, boolean)</code>
 * method.
 * </p>
 * 
 * <p>
 * <code>Trigger</code> s can then be defined to fire individual <code>Job</code>
 * instances based on given schedules. <code>SimpleTrigger</code> s are most
 * useful for one-time firings, or firing at an exact moment in time, with N
 * repeats with a given delay between them. <code>CronTrigger</code> s allow
 * scheduling based on time of day, day of week, day of month, and month of
 * year.
 * </p>
 * 
 * <p>
 * <code>Job</code> s and <code>Trigger</code> s have a name and group
 * associated with them, which should uniquely identify them within a single
 * <code>{@link Scheduler}</code>. The 'group' feature may be useful for
 * creating logical groupings or categorizations of <code>Jobs</code> s and
 * <code>Triggers</code>s. If you don't have need for assigning a group to a
 * given <code>Jobs</code> of <code>Triggers</code>, then you can use the
 * <code>DEFAULT_GROUP</code> constant defined on this interface.
 * </p>
 * 
 * <p>
 * Stored <code>Job</code> s can also be 'manually' triggered through the use
 * of the <code>triggerJob(String jobName, String jobGroup)</code> function.
 * </p>
 * 
 * <p>
 * Client programs may also be interested in the 'listener' interfaces that are
 * available from Quartz. The <code>{@link JobListener}</code> interface
 * provides notifications of <code>Job</code> executions. The <code>{@link TriggerListener}</code>
 * interface provides notifications of <code>Trigger</code> firings. The
 * <code>{@link SchedulerListener}</code> interface provides notifications of
 * <code>Scheduler</code> events and errors.
 * </p>
 * 
 * <p>
 * The setup/configuration of a <code>Scheduler</code> instance is very
 * customizable. Please consult the documentation distributed with Quartz.
 * </p>
 * 
 * @see Job
 * @see JobDetail
 * @see Trigger
 * @see JobListener
 * @see TriggerListener
 * @see SchedulerListener
 * 
 * @author James House
 * @author Sharada Jambula
 */
public interface Scheduler {

    /*
     * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     * 
     * Constants.
     * 
     * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     */

    /**
     * <p>
     * A (possibly) usefull constant that can be used for specifying the group
     * that <code>Job</code> and <code>Trigger</code> instances belong to.
     * </p>
     */
    public static final String DEFAULT_GROUP = "DEFAULT";

    /**
     * <p>
     * A constant <code>Trigger</code> group name used internally by the
     * scheduler - clients should not use the value of this constant
     * ("MANUAL_TRIGGER") for thename of a <code>Trigger</code>'s group.
     * </p>
     */
    public static final String DEFAULT_MANUAL_TRIGGERS = "MANUAL_TRIGGER";

    /**
     * <p>
     * A constant <code>Trigger</code> group name used internally by the
     * scheduler - clients should not use the value of this constant
     * ("RECOVERING_JOBS") for thename of a <code>Trigger</code>'s group.
     * </p>
     */
    public static final String DEFAULT_RECOVERY_GROUP = "RECOVERING_JOBS";

    /**
     * <p>
     * A constant <code>Trigger</code> group name used internally by the
     * scheduler - clients should not use the value of this constant
     * ("FAILED_OVER_JOBS") for thename of a <code>Trigger</code>'s group.
     * </p>
     */
    public static final String DEFAULT_FAIL_OVER_GROUP = "FAILED_OVER_JOBS";

    /*
     * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     * 
     * Interface.
     * 
     * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     */

    /**
     * <p>
     * Returns the name of the <code>Scheduler</code>.
     * </p>
     */
    public String getSchedulerName() throws SchedulerException;

    /**
     * <p>
     * Returns the instance Id of the <code>Scheduler</code>.
     * </p>
     */
    public String getSchedulerInstanceId() throws SchedulerException;

    /**
     * <p>
     * Returns the <code>SchedulerContext</code> of the <code>Scheduler</code>.
     * </p>
     */
    public SchedulerContext getContext() throws SchedulerException;

    ///////////////////////////////////////////////////////////////////////////
    ///
    /// Schedululer State Management Methods
    ///
    ///////////////////////////////////////////////////////////////////////////

    /**
     * <p>
     * Starts the <code>Scheduler</code>'s threads that fire <code>{@link Trigger}s</code>.
     * When a scheduler is first created it is in "stand-by" mode, and will not
     * fire triggers.  The scheduler can also be put into stand-by mode by
     * calling the <code>standby()</code> method. 
     * </p>
     * 
     * <p>
     * The misfire/recovery process will be started, if it is the initial call
     * to this method on this scheduler instance.
     * </p>
     * 
     * @throws SchedulerException
     *           if <code>shutdown()</code> has been called, or there is an
     *           error within the <code>Scheduler</code>.
     * 
     * @see #standby
     * @see #shutdown
     */
    public void start() throws SchedulerException;

    /**
     * <p>
     * Temporarily halts the <code>Scheduler</code>'s firing of <code>{@link Trigger}s</code>.
     * </p>
     * 
     * <p>
     * When <code>start()</code> is called (to bring the scheduler out of 
     * stand-by mode), trigger misfire instructions will NOT be applied
     * during the execution of the <code>start()</code> method - any misfires 
     * will be detected immediately afterward (by the <code>JobStore</code>'s 
     * normal process).
     * </p>
     * 
     * <p>
     * The scheduler is not destroyed, and can be re-started at any time.
     * </p>
     * 
     * @see #start()
     * @see #pauseAll()
     */
    public void standby() throws SchedulerException;

    /**
     * @deprecated replaced by better-named standby() method.
     * @see #standby()
     */
    public void pause() throws SchedulerException;

    /**
     * <p>
     * Reports whether the <code>Scheduler</code> is in stand-by mode.
     * </p>
     * 
     * @see #standby()
     * @see #start()
     */
    public boolean isInStandbyMode() throws SchedulerException;

    /**
     * @deprecated
     * @see #isInStandbyMode() 
     */
    public boolean isPaused() throws SchedulerException;

    /**
     * <p>
     * Halts the <code>Scheduler</code>'s firing of <code>{@link Trigger}s</code>,
     * and cleans up all resources associated with the Scheduler. Equivalent to
     * <code>shutdown(false)</code>.
     * </p>
     * 
     * <p>
     * The scheduler cannot be re-started.
     * </p>
     * 
     * @see #shutdown(boolean)
     */
    public void shutdown() throws SchedulerException;

    /**
     * <p>
     * Halts the <code>Scheduler</code>'s firing of <code>{@link Trigger}s</code>,
     * and cleans up all resources associated with the Scheduler.
     * </p>
     * 
     * <p>
     * The scheduler cannot be re-started.
     * </p>
     * 
     * @param waitForJobsToComplete
     *          if <code>true</code> the scheduler will not allow this method
     *          to return until all currently executing jobs have completed.
     * 
     * @see #shutdown
     */
    public void shutdown(boolean waitForJobsToComplete)
            throws SchedulerException;

    /**
     * <p>
     * Reports whether the <code>Scheduler</code> has been shutdown.
     * </p>
     */
    public boolean isShutdown() throws SchedulerException;

    /**
     * <p>
     * Get a <code>SchedulerMetaData</code> object describiing the settings
     * and capabilities of the scheduler instance.
     * </p>
     * 
     * <p>
     * Note that the data returned is an 'instantaneous' snap-shot, and that as
     * soon as it's returned, the meta data values may be different.
     * </p>
     */
    public SchedulerMetaData getMetaData() throws SchedulerException;

    /**
     * <p>
     * Return a list of <code>JobExecutionContext</code> objects that
     * represent all currently executing Jobs.
     * </p>
     * 
     * <p>
     * Note that the list returned is an 'instantaneous' snap-shot, and that as
     * soon as it's returned, the true list of executing jobs may be different.
     * Also please read the doc associated with <code>JobExecutionContext</code>-
     * especially if you're using RMI.
     * </p>
     * 
     * @see JobExecutionContext
     */
    public List getCurrentlyExecutingJobs() throws SchedulerException;

    /**
     * <p>