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Java > Open Source Codes > org > apache > commons > configuration > reloading > FileChangedReloadingStrategy


1 /*
2  * Copyright 2001-2005 The Apache Software Foundation.
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License")
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16
17 package org.apache.commons.configuration.reloading;
18
19 import org.apache.commons.configuration.FileConfiguration;
20
21 /**
22  * A reloading strategy that will reload the configuration every time its
23  * underlying file is changed. The file is not reloaded more than once
24  * every 5 seconds by default, this time can be changed by setting the refresh
25  * delay. This strategy only works with FileConfiguration instances.
26  *
27  * @author Emmanuel Bourg
28  * @version $Revision: 155945 $, $Date: 2005-03-02 20:29:39 +0100 (Mi, 02 Mrz 2005) $
29  * @since 1.1
30  */
31 public class FileChangedReloadingStrategy implements ReloadingStrategy
32 {
33     protected FileConfiguration configuration;
34
35     /** The last time the configuration file was modified. */
36     protected long lastModified;
37
38     /** The last time the file was checked for changes. */
39     protected long lastChecked;
40
41     /** The minimum delay in milliseconds between checks. */
42     protected long refreshDelay = 5000;
43
44     public void setConfiguration(FileConfiguration configuration)
45     {
46         this.configuration = configuration;
47     }
48
49     public void init()
50     {
51         updateLastModified();
52     }
53
54     public boolean reloadingRequired()
55     {
56         boolean reloading = false;
57
58         long now = System.currentTimeMillis();
59
60         if ((now > lastChecked + refreshDelay) && hasChanged())
61         {
62             lastChecked = now;
63             reloading = true;
64         }
65
66         return reloading;
67     }
68
69     public void reloadingPerformed()
70     {
71         updateLastModified();
72     }
73
74     /**
75      * Return the minimal time in milliseconds between two reloadings.
76      */
77     public long getRefreshDelay()
78     {
79         return refreshDelay;
80     }
81
82     /**
83      * Set the minimal time between two reloadings.
84      *
85      * @param refreshDelay refresh delay in milliseconds
86      */
87     public void setRefreshDelay(long refreshDelay)
88     {
89         this.refreshDelay = refreshDelay;
90     }
91
92     /**
93      * Update the last modified time.
94      */
95     protected void updateLastModified()
96     {
97         lastModified = configuration.getFile().lastModified();
98     }
99
100     /**
101      * Check if the configuration has changed since the last time it was loaded.
102      */
103     protected boolean hasChanged()
104     {
105         if (!configuration.getFile().exists())
106         {
107             return false;
108         }
109
110         return (configuration.getFile().lastModified() > lastModified);
111     }
112
113 }
114
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