001// Licensed under the Apache License, Version 2.0 (the "License");
002// you may not use this file except in compliance with the License.
003// You may obtain a copy of the License at
004//
005// http://www.apache.org/licenses/LICENSE-2.0
006//
007// Unless required by applicable law or agreed to in writing, software
008// distributed under the License is distributed on an "AS IS" BASIS,
009// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
010// See the License for the specific language governing permissions and
011// limitations under the License.
012
013package org.apache.tapestry5.ioc.services.cron;
014
015/**
016 * Used with {@link PeriodicExecutor} to control the schedule for when jobs execute.
017 */
018public interface Schedule
019{
020    /**
021     * For a newly created job, what is the start time for the job.  Often, the current clock time is returned, to start
022     * a job as soon as possible.
023     *
024     * @return start time for new job, in system clock millis
025     */
026    long firstExecution();
027
028    /**
029     * Computes the next execution time for a job.
030     *
031     * @param previousExecution time of previous execution (in system clock millis)
032     * @return time of next execution (in system clock millis) or a value <= 0 to cancel the job's execution
033     */
034    long nextExecution(long previousExecution);
035}