1
2 /*
3 * Copyright 2004-2005 OpenSymphony
4 *
5 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
6 * use this file except in compliance with the License. You may obtain a copy
7 * of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
13 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
14 * License for the specific language governing permissions and limitations
15 * under the License.
16 *
17 */
18
19 /*
20 * Previously Copyright (c) 2001-2004 James House
21 */
22 package org.quartz;
23
24 /**
25 * <p>
26 * The interface to be implemented by <code>{@link Job}s</code> that provide a
27 * mechanism for having their execution interrupted. It is NOT a requirment
28 * for jobs to implement this interface - in fact, for most people, none of
29 * their jobs will.
30 * </p>
31 *
32 * <p>
33 * The means of actually interrupting the Job must be implemented within the
34 * <code>Job</code> itself (the <code>interrupt()</code> method of this
35 * interface is simply a means for the scheduler to inform the <code>Job</code>
36 * that a request has been made for it to be interrupted). The mechanism that
37 * your jobs use to interrupt themselves might vary between implementations.
38 * However the principle idea in any implementation should be to have the
39 * body of the job's <code>execute(..)</code> periodically check some flag to
40 * see if an interruption has been requested, and if the flag is set, somehow
41 * abort the performance of the rest of the job's work. An example of
42 * interrupting a job can be found in the java source for the class
43 * <code>org.quartz.examples.DumbInterruptableJob</code>. It is legal to use
44 * some combination of <code>wait()</code> and <code>notify()</code>
45 * synchronization within <code>interrupt()</code> and <code>execute(..)</code>
46 * in order to have the <code>interrupt()</code> method block until the
47 * <code>execute(..)</code> signals that it has noticed the set flag.
48 * </p>
49 *
50 * <p>
51 * If the Job performs some form of blocking I/O or similar functions, you may
52 * want to consider having the <code>Job.execute(..)</code> method store a
53 * reference to the calling <code>Thread</code> as a member variable. Then the
54 * impplementation of this interfaces <code>interrupt()</code> method can call
55 * <code>interrupt()</code> on that Thread. Before attempting this, make
56 * sure that you fully understand what <code>java.lang.Thread.interrupt()</code>
57 * does and doesn't do. Also make sure that you clear the Job's member
58 * reference to the Thread when the execute(..) method exits (preferrably in a
59 * <code>finally</code> block.
60 * </p>
61 *
62 * <p>
63 * See Example 7 (org.quartz.examples.example7.DumbInterruptableJob) for a simple
64 * implementation demonstration.
65 * </p>
66 * @see Job
67 * @see StatefulJob
68 * @see Scheduler#interrupt(String, String)
69 *
70 * @author James House
71 */
72 public interface InterruptableJob extends Job {
73
74 /*
75 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
76 *
77 * Interface.
78 *
79 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
80 */
81
82 /**
83 * <p>
84 * Called by the <code>{@link Scheduler}</code> when a user
85 * interrupts the <code>Job</code>.
86 * </p>
87 *
88 * @throws UnableToInterruptJobException
89 * if there is an exception while interrupting the job.
90 */
91 void interrupt()
92 throws UnableToInterruptJobException;
93 }
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