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Java > Open Source Codes > org > apache > turbine > services > schedule > JobQueue


1 package org.apache.turbine.services.schedule;
2
3 /*
4  * Copyright 2001-2004 The Apache Software Foundation.
5  *
6  * Licensed under the Apache License, Version 2.0 (the "License")
7  * you may not use this file except in compliance with the License.
8  * You may obtain a copy of the License at
9  *
10  * http://www.apache.org/licenses/LICENSE-2.0
11  *
12  * Unless required by applicable law or agreed to in writing, software
13  * distributed under the License is distributed on an "AS IS" BASIS,
14  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15  * See the License for the specific language governing permissions and
16  * limitations under the License.
17  */
18
19 import java.util.Collections JavaDoc;
20 import java.util.Comparator JavaDoc;
21 import java.util.List JavaDoc;
22 import java.util.Vector JavaDoc;
23
24 import org.apache.turbine.util.TurbineException;
25
26 /**
27  * Queue for the scheduler.
28  *
29  * @author <a HREF="mailto:mbryson@mont.mindspring.com">Dave Bryson</a>
30  * @author <a HREF="mailto:quintonm@bellsouth.net">Quinton McCombs</a>
31  * @version $Id: JobQueue.java,v 1.5.2.2 2004/05/20 03:06:49 seade Exp $
32  */
33 public class JobQueue
34 {
35     /**
36      * The queue of <code>JobEntry</code> objects.
37      */
38     private Vector JavaDoc queue = null;
39
40     /**
41      * Creates a new instance.
42      */
43     public JobQueue()
44     {
45         queue = new Vector JavaDoc(10);
46     }
47
48     /**
49      * Return the next job off the top of the queue, or <code>null</code> if
50      * there are no jobs in the queue.
51      *
52      * @return The next job in the queue.
53      */
54     public JobEntry getNext()
55     {
56         if (queue.size() > 0)
57         {
58             return (JobEntry) queue.elementAt(0);
59         }
60         else
61         {
62             return null;
63         }
64     }
65
66     /**
67      * Return a specific job.
68      *
69      * @param je The JobEntry we are looking for.
70      * @return A JobEntry.
71      */
72     public JobEntry getJob(JobEntry je)
73     {
74         int index = -1;
75
76         if (je != null)
77         {
78             index = queue.indexOf(je);
79         }
80
81         if (index < 0)
82         {
83             return null;
84         }
85         else
86         {
87             return (JobEntry) queue.elementAt(index);
88         }
89     }
90
91     /**
92      * List jobs in the queue. This is used by the scheduler UI.
93      *
94      * @return A Vector of <code>JobEntry</code> objects.
95      */
96     public Vector JavaDoc list()
97     {
98         if (queue != null && queue.size() > 0)
99         {
100             return (Vector JavaDoc) queue.clone();
101         }
102         else
103         {
104             return null;
105         }
106     }
107
108     /**
109      * Add a job to the queue.
110      *
111      * @param je A JobEntry job.
112      */
113     public synchronized void add(JobEntry je)
114     {
115         queue.addElement(je);
116         sortQueue();
117     }
118
119     /**
120      * Batch load jobs. Retains any already enqueued jobs. Called on
121      * <code>SchedulerService</code> start-up.
122      *
123      * @param jobEntries A list of the <code>JobEntry</code> objects to load.
124      */
125     public synchronized void batchLoad(List JavaDoc jobEntries)
126     {
127         if (jobEntries != null)
128         {
129             queue.addAll(jobEntries);
130             sortQueue();
131         }
132
133     }
134
135     /**
136      * Remove a job from the queue.
137      *
138      * @param je A JobEntry with the job to remove.
139      */
140     public synchronized void remove(JobEntry je)
141     {
142         queue.removeElement(je);
143         sortQueue();
144     }
145
146     /**
147      * Modify a job on the queue.
148      *
149      * @param je A JobEntry with the job to modify
150      */
151     public synchronized void modify(JobEntry je)
152             throws TurbineException
153     {
154         remove(je);
155         je.calcRunTime();
156         this.add(je);
157         sortQueue();
158     }
159
160     /**
161      * Update the job for its next run time.
162      *
163      * @param je A JobEntry to be updated.
164      * @exception TurbineException a generic exception.
165      */
166     public synchronized void updateQueue(JobEntry je)
167             throws TurbineException
168     {
169         je.calcRunTime();
170         sortQueue();
171     }
172
173     /**
174      * Re-sort the existing queue. Consumers of this method should be
175      * <code>synchronized</code>.
176      */
177     private void sortQueue()
178     {
179         Comparator JavaDoc aComparator = new Comparator JavaDoc()
180         {
181             public int compare(Object JavaDoc o1, Object JavaDoc o2)
182             {
183                 Long JavaDoc time1 = new Long JavaDoc(((JobEntry) o1).getNextRuntime());
184                 Long JavaDoc time2 = new Long JavaDoc(((JobEntry) o2).getNextRuntime());
185                 return (time1.compareTo(time2));
186             }
187         };
188
189         Collections.sort(queue, aComparator);
190     }
191 }
192
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