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org.apache.commons.configuration.reloading.FileChangedReloadingStrategy |
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1 | /* |
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2 | * Copyright 2001-2005 The Apache Software Foundation. |
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3 | * |
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4 | * Licensed under the Apache License, Version 2.0 (the "License") |
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5 | * you may not use this file except in compliance with the License. |
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6 | * You may obtain a copy of the License at |
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7 | * |
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8 | * http://www.apache.org/licenses/LICENSE-2.0 |
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9 | * |
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10 | * Unless required by applicable law or agreed to in writing, software |
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11 | * distributed under the License is distributed on an "AS IS" BASIS, |
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12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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13 | * See the License for the specific language governing permissions and |
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14 | * limitations under the License. |
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15 | */ |
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16 | ||
17 | package org.apache.commons.configuration.reloading; |
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18 | ||
19 | import java.io.File; |
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20 | import java.net.MalformedURLException; |
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21 | import java.net.URL; |
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22 | ||
23 | import org.apache.commons.configuration.ConfigurationUtils; |
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24 | import org.apache.commons.configuration.FileConfiguration; |
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25 | ||
26 | /** |
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27 | * <p>A reloading strategy that will reload the configuration every time its |
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28 | * underlying file is changed.</p> |
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29 | * <p>This reloading strategy does not actively monitor a configuration file, |
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30 | * but is triggered by its associated configuration whenever properties are |
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31 | * accessed. It then checks the configuration file's last modification date |
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32 | * and causes a reload if this has changed.</p> |
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33 | * <p>To avoid permanent disc access on successive property lookups a refresh |
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34 | * delay can be specified. This has the effect that the configuration file's |
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35 | * last modification date is only checked once in this delay period. The default |
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36 | * value for this refresh delay is 5 seconds.</p> |
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37 | * <p>This strategy only works with FileConfiguration instances.</p> |
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38 | * |
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39 | * @author Emmanuel Bourg |
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40 | * @version $Revision$, $Date: 2005-10-10 21:26:46 +0200 (Mon, 10 Oct 2005) $ |
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41 | * @since 1.1 |
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42 | */ |
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43 | 48 | public class FileChangedReloadingStrategy implements ReloadingStrategy |
44 | { |
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45 | /** Constant for the jar URL protocol.*/ |
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46 | private static final String JAR_PROTOCOL = "jar"; |
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47 | ||
48 | /** Constant for the default refresh delay.*/ |
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49 | private static final int DEFAULT_REFRESH_DELAY = 5000; |
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50 | ||
51 | /** Stores a reference to the configuration to be monitored.*/ |
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52 | protected FileConfiguration configuration; |
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53 | ||
54 | /** The last time the configuration file was modified. */ |
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55 | protected long lastModified; |
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56 | ||
57 | /** The last time the file was checked for changes. */ |
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58 | protected long lastChecked; |
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59 | ||
60 | /** The minimum delay in milliseconds between checks. */ |
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61 | 24 | protected long refreshDelay = DEFAULT_REFRESH_DELAY; |
62 | ||
63 | public void setConfiguration(FileConfiguration configuration) |
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64 | { |
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65 | 21 | this.configuration = configuration; |
66 | 21 | } |
67 | ||
68 | public void init() |
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69 | { |
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70 | 27 | updateLastModified(); |
71 | 27 | } |
72 | ||
73 | public boolean reloadingRequired() |
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74 | { |
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75 | 30 | boolean reloading = false; |
76 | ||
77 | 30 | long now = System.currentTimeMillis(); |
78 | ||
79 | 30 | if (now > lastChecked + refreshDelay) |
80 | { |
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81 | 21 | lastChecked = now; |
82 | 21 | if (hasChanged()) |
83 | { |
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84 | 9 | reloading = true; |
85 | } |
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86 | } |
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87 | ||
88 | 30 | return reloading; |
89 | } |
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90 | ||
91 | public void reloadingPerformed() |
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92 | { |
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93 | 9 | updateLastModified(); |
94 | 9 | } |
95 | ||
96 | /** |
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97 | * Return the minimal time in milliseconds between two reloadings. |
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98 | * |
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99 | * @return the refresh delay (in milliseconds) |
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100 | */ |
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101 | public long getRefreshDelay() |
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102 | { |
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103 | 3 | return refreshDelay; |
104 | } |
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105 | ||
106 | /** |
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107 | * Set the minimal time between two reloadings. |
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108 | * |
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109 | * @param refreshDelay refresh delay in milliseconds |
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110 | */ |
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111 | public void setRefreshDelay(long refreshDelay) |
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112 | { |
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113 | 12 | this.refreshDelay = refreshDelay; |
114 | 12 | } |
115 | ||
116 | /** |
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117 | * Update the last modified time. |
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118 | */ |
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119 | protected void updateLastModified() |
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120 | { |
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121 | 36 | File file = getFile(); |
122 | 36 | if (file != null) |
123 | { |
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124 | 36 | lastModified = file.lastModified(); |
125 | } |
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126 | 36 | } |
127 | ||
128 | /** |
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129 | * Check if the configuration has changed since the last time it was loaded. |
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130 | * |
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131 | * @return a flag whether the configuration has changed |
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132 | */ |
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133 | protected boolean hasChanged() |
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134 | { |
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135 | 21 | File file = getFile(); |
136 | 21 | if (file == null || !file.exists()) |
137 | { |
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138 | 3 | return false; |
139 | } |
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140 | ||
141 | 18 | return file.lastModified() > lastModified; |
142 | } |
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143 | ||
144 | /** |
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145 | * Returns the file that is monitored by this strategy. Note that the return |
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146 | * value can be <b>null </b> under some circumstances. |
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147 | * |
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148 | * @return the monitored file |
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149 | */ |
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150 | protected File getFile() |
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151 | { |
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152 | 63 | return (configuration.getURL() != null) ? fileFromURL(configuration |
153 | .getURL()) : configuration.getFile(); |
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154 | } |
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155 | ||
156 | /** |
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157 | * Helper method for transforming a URL into a file object. This method |
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158 | * handles file: and jar: URLs. |
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159 | * |
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160 | * @param url the URL to be converted |
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161 | * @return the resulting file or <b>null </b> |
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162 | */ |
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163 | private File fileFromURL(URL url) |
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164 | { |
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165 | 57 | if (JAR_PROTOCOL.equals(url.getProtocol())) |
166 | { |
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167 | 6 | String path = url.getPath(); |
168 | try |
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169 | { |
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170 | 6 | return ConfigurationUtils.fileFromURL(new URL(path.substring(0, |
171 | path.indexOf('!')))); |
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172 | } |
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173 | catch (MalformedURLException mex) |
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174 | { |
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175 | 0 | return null; |
176 | } |
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177 | } |
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178 | else |
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179 | { |
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180 | 51 | return ConfigurationUtils.fileFromURL(url); |
181 | } |
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182 | } |
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183 | } |
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