001    // Copyright 2011 The Apache Software Foundation
002    //
003    // Licensed under the Apache License, Version 2.0 (the "License");
004    // you may not use this file except in compliance with the License.
005    // You may obtain a copy of the License at
006    //
007    // http://www.apache.org/licenses/LICENSE-2.0
008    //
009    // Unless required by applicable law or agreed to in writing, software
010    // distributed under the License is distributed on an "AS IS" BASIS,
011    // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
012    // See the License for the specific language governing permissions and
013    // limitations under the License.
014    
015    package org.apache.tapestry5.ioc.services.cron;
016    
017    /**
018     * Used with {@link PeriodicExecutor} to control the schedule for when jobs execute.
019     */
020    public interface Schedule
021    {
022        /**
023         * For a newly created job, what is the start time for the job.  Often, the current clock time is returned, to start
024         * a job as soon as possible.
025         *
026         * @return start time for new job, in system clock millis
027         */
028        long firstExecution();
029    
030        /**
031         * Computes the next execution time for a job.
032         *
033         * @param previousExecution time of previous execution (in system clock millis)
034         * @return time of next execution (in system clock millis)
035         */
036        long nextExecution(long previousExecution);
037    }