001 /*
002 * Copyright 2004-2005 Stephen J. McConnell.
003 * Copyright 1999-2004 The Apache Software Foundation
004 *
005 * Licensed under the Apache License, Version 2.0 (the "License");
006 * you may not use this file except in compliance with the License.
007 * You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
014 * implied.
015 *
016 * See the License for the specific language governing permissions and
017 * limitations under the License.
018 */
019 package net.dpml.i18n;
020
021 import java.lang.ref.WeakReference;
022 import java.util.HashMap;
023 import java.util.Locale;
024
025 /**
026 * Manager for resources.
027 *
028 * @author <a href="http://www.dpml.net">Digital Product Meta Library</a>
029 * @version 1.0.0
030 */
031 public final class ResourceManager
032 {
033 /**
034 * Permission needed to clear complete cache.
035 */
036 private static final RuntimePermission CLEAR_CACHE_PERMISSION =
037 new RuntimePermission( "i18n.clearCompleteCache" );
038
039 /**
040 * Resource lookup table.
041 */
042 private static final HashMap RESOURCES = new HashMap();
043
044 /**
045 * Retrieve resource with specified basename.
046 *
047 * @param baseName the basename
048 * @return the Resources
049 */
050 public static final Resources getBaseResources( final String baseName )
051 {
052 return getBaseResources( baseName, null );
053 }
054
055 /**
056 * Retrieve resource with specified basename.
057 *
058 * @param baseName the basename
059 * @param classLoader the classLoader to load resources from
060 * @return the Resources
061 */
062 public static final synchronized Resources getBaseResources(
063 final String baseName, final ClassLoader classLoader )
064 {
065 Resources resources = getCachedResource( baseName );
066 if( null == resources )
067 {
068 resources = new Resources( baseName, classLoader );
069 putCachedResource( baseName, resources );
070 }
071
072 return resources;
073 }
074
075 /**
076 * Retrieve resource with specified basename.
077 *
078 * @param baseName the basename
079 * @param locale the locale
080 * @param classLoader the classLoader to load resources from
081 * @return the Resources
082 */
083 public static final synchronized Resources getBaseResources(
084 final String baseName, final Locale locale, final ClassLoader classLoader )
085 {
086 Resources resources = getCachedResource( baseName + "_" + locale.hashCode() );
087 if( null == resources )
088 {
089 resources = new Resources( baseName, locale, classLoader );
090 putCachedResource( baseName + "_" + locale.hashCode(), resources );
091 }
092
093 return resources;
094 }
095
096 /**
097 * Clear the cache of all resources currently loaded into the
098 * system. This method is useful if you need to dump the complete
099 * cache and because part of the application is reloading and
100 * thus the resources may need to be reloaded.
101 *
102 * <p>Note that the caller must have been granted the
103 * "i18n.clearCompleteCache" {@link RuntimePermission} or
104 * else a security exception will be thrown.</p>
105 *
106 * @throws SecurityException if the caller does not have
107 * permission to clear cache
108 */
109 public static final synchronized void clearResourceCache()
110 throws SecurityException
111 {
112 final SecurityManager sm = System.getSecurityManager();
113 if( null != sm )
114 {
115 sm.checkPermission( CLEAR_CACHE_PERMISSION );
116 }
117
118 RESOURCES.clear();
119 }
120
121 /**
122 * Cache specified resource in weak reference.
123 *
124 * @param baseName the resource key
125 * @param resources the resources object
126 */
127 private static final synchronized void putCachedResource(
128 final String baseName, final Resources resources )
129 {
130 RESOURCES.put( baseName, new WeakReference( resources ) );
131 }
132
133 /**
134 * Retrieve cached resource.
135 *
136 * @param baseName the resource key
137 * @return resources the resources object
138 */
139 private static final synchronized Resources getCachedResource( final String baseName )
140 {
141 final WeakReference weakReference =
142 (WeakReference) RESOURCES.get( baseName );
143 if( null == weakReference )
144 {
145 return null;
146 }
147 else
148 {
149 return (Resources) weakReference.get();
150 }
151 }
152
153 /**
154 * Retrieve resource for specified name.
155 * The basename is determined by name postfixed with ".Resources".
156 *
157 * @param name the name to use when looking up resources
158 * @return the Resources
159 */
160 public static final Resources getResources( final String name )
161 {
162 return getBaseResources( name + ".Resources" );
163 }
164
165 /**
166 * Retrieve resource for specified Classes package.
167 * The basename is determined by name of classes package
168 * postfixed with ".Resources".
169 *
170 * @param clazz the Class
171 * @return the Resources
172 */
173 public static final Resources getPackageResources( final Class clazz )
174 {
175 return getBaseResources( getPackageResourcesBaseName( clazz ), clazz.getClassLoader() );
176 }
177
178 /**
179 * Retrieve resource for specified Classes package.
180 * The basename is determined by name of classes package
181 * postfixed with ".Resources".
182 *
183 * @param clazz the Class
184 * @param locale the locale
185 * @return the Resources
186 */
187 public static final Resources getPackageResources( final Class clazz, Locale locale )
188 {
189 return getBaseResources( getPackageResourcesBaseName( clazz ), locale, clazz.getClassLoader() );
190 }
191
192 /**
193 * Retrieve resource for specified Class.
194 * The basename is determined by name of Class
195 * postfixed with "Resources".
196 *
197 * @param clazz the Class
198 * @return the Resources
199 */
200 public static final Resources getClassResources( final Class clazz )
201 {
202 return getBaseResources( getClassResourcesBaseName( clazz ), clazz.getClassLoader() );
203 }
204
205 /**
206 * Retrieve resource for specified Class.
207 * The basename is determined by name of Class
208 * postfixed with "Resources".
209 *
210 * @param clazz the Class
211 * @param locale the requested Locale.
212 * @return the Resources
213 */
214 public static final Resources getClassResources( final Class clazz, Locale locale )
215 {
216 return getBaseResources( getClassResourcesBaseName( clazz ), locale, clazz.getClassLoader() );
217 }
218
219 /**
220 * Retrieve resource basename for specified Classes package.
221 * The basename is determined by name of classes package
222 * postfixed with ".Resources".
223 *
224 * @param clazz the Class
225 * @return the resource basename
226 */
227 public static final String getPackageResourcesBaseName( final Class clazz )
228 {
229 final Package pkg = clazz.getPackage();
230
231 String baseName;
232 if( null == pkg )
233 {
234 final String name = clazz.getName();
235 if( -1 == name.lastIndexOf( "." ) )
236 {
237 baseName = "Resources";
238 }
239 else
240 {
241 baseName = name.substring( 0, name.lastIndexOf( "." ) ) + ".Resources";
242 }
243 }
244 else
245 {
246 baseName = pkg.getName() + ".Resources";
247 }
248
249 return baseName;
250 }
251
252 /**
253 * Retrieve resource basename for specified Class.
254 * The basename is determined by name of Class
255 * postfixed with "Resources".
256 *
257 * @param clazz the Class
258 * @return the resource basename
259 */
260 public static final String getClassResourcesBaseName( final Class clazz )
261 {
262 return clazz.getName() + "Resources";
263 }
264
265 /**
266 * Private Constructor to block instantiation.
267 */
268 private ResourceManager()
269 {
270 }
271 }