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org.apache.commons.configuration.reloading.FileChangedReloadingStrategy	97%	95%

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 java.io.File;
20		import java.net.MalformedURLException;
21		import java.net.URL;
22
23		import org.apache.commons.configuration.ConfigurationUtils;
24		import org.apache.commons.configuration.FileConfiguration;
25
26		/**
27		* <p>A reloading strategy that will reload the configuration every time its
28		* underlying file is changed.</p>
29		* <p>This reloading strategy does not actively monitor a configuration file,
30		* but is triggered by its associated configuration whenever properties are
31		* accessed. It then checks the configuration file's last modification date
32		* and causes a reload if this has changed.</p>
33		* <p>To avoid permanent disc access on successive property lookups a refresh
34		* delay can be specified. This has the effect that the configuration file's
35		* last modification date is only checked once in this delay period. The default
36		* value for this refresh delay is 5 seconds.</p>
37		* <p>This strategy only works with FileConfiguration instances.</p>
38		*
39		* @author Emmanuel Bourg
40		* @version $Revision$, $Date: 2005-10-10 21:26:46 +0200 (Mon, 10 Oct 2005) $
41		* @since 1.1
42		*/
43	48	public class FileChangedReloadingStrategy implements ReloadingStrategy
44		{
45		/** Constant for the jar URL protocol.*/
46		private static final String JAR_PROTOCOL = "jar";
47
48		/** Constant for the default refresh delay.*/
49		private static final int DEFAULT_REFRESH_DELAY = 5000;
50
51		/** Stores a reference to the configuration to be monitored.*/
52		protected FileConfiguration configuration;
53
54		/** The last time the configuration file was modified. */
55		protected long lastModified;
56
57		/** The last time the file was checked for changes. */
58		protected long lastChecked;
59
60		/** The minimum delay in milliseconds between checks. */
61	24	protected long refreshDelay = DEFAULT_REFRESH_DELAY;
62
63		public void setConfiguration(FileConfiguration configuration)
64		{
65	21	this.configuration = configuration;
66	21	}
67
68		public void init()
69		{
70	27	updateLastModified();
71	27	}
72
73		public boolean reloadingRequired()
74		{
75	30	boolean reloading = false;
76
77	30	long now = System.currentTimeMillis();
78
79	30	if (now > lastChecked + refreshDelay)
80		{
81	21	lastChecked = now;
82	21	if (hasChanged())
83		{
84	9	reloading = true;
85		}
86		}
87
88	30	return reloading;
89		}
90
91		public void reloadingPerformed()
92		{
93	9	updateLastModified();
94	9	}
95
96		/**
97		* Return the minimal time in milliseconds between two reloadings.
98		*
99		* @return the refresh delay (in milliseconds)
100		*/
101		public long getRefreshDelay()
102		{
103	3	return refreshDelay;
104		}
105
106		/**
107		* Set the minimal time between two reloadings.
108		*
109		* @param refreshDelay refresh delay in milliseconds
110		*/
111		public void setRefreshDelay(long refreshDelay)
112		{
113	12	this.refreshDelay = refreshDelay;
114	12	}
115
116		/**
117		* Update the last modified time.
118		*/
119		protected void updateLastModified()
120		{
121	36	File file = getFile();
122	36	if (file != null)
123		{
124	36	lastModified = file.lastModified();
125		}
126	36	}
127
128		/**
129		* Check if the configuration has changed since the last time it was loaded.
130		*
131		* @return a flag whether the configuration has changed
132		*/
133		protected boolean hasChanged()
134		{
135	21	File file = getFile();
136	21	if (file == null || !file.exists())
137		{
138	3	return false;
139		}
140
141	18	return file.lastModified() > lastModified;
142		}
143
144		/**
145		* Returns the file that is monitored by this strategy. Note that the return
146		* value can be <b>null </b> under some circumstances.
147		*
148		* @return the monitored file
149		*/
150		protected File getFile()
151		{
152	63	return (configuration.getURL() != null) ? fileFromURL(configuration
153		.getURL()) : configuration.getFile();
154		}
155
156		/**
157		* Helper method for transforming a URL into a file object. This method
158		* handles file: and jar: URLs.
159		*
160		* @param url the URL to be converted
161		* @return the resulting file or <b>null </b>
162		*/
163		private File fileFromURL(URL url)
164		{
165	57	if (JAR_PROTOCOL.equals(url.getProtocol()))
166		{
167	6	String path = url.getPath();
168		try
169		{
170	6	return ConfigurationUtils.fileFromURL(new URL(path.substring(0,
171		path.indexOf('!'))));
172		}
173		catch (MalformedURLException mex)
174		{
175	0	return null;
176		}
177		}
178		else
179		{
180	51	return ConfigurationUtils.fileFromURL(url);
181		}
182		}
183		}

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