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1   /*
2    * $Id: MessageResourcesFactory.java 471754 2006-11-06 14:55:09Z husted $
3    *
4    * Licensed to the Apache Software Foundation (ASF) under one
5    * or more contributor license agreements.  See the NOTICE file
6    * distributed with this work for additional information
7    * regarding copyright ownership.  The ASF licenses this file
8    * to you under the Apache License, Version 2.0 (the
9    * "License"); you may not use this file except in compliance
10   * with the License.  You may obtain a copy of the License at
11   *
12   *  http://www.apache.org/licenses/LICENSE-2.0
13   *
14   * Unless required by applicable law or agreed to in writing,
15   * software distributed under the License is distributed on an
16   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
17   * KIND, either express or implied.  See the License for the
18   * specific language governing permissions and limitations
19   * under the License.
20   */
21  package org.apache.struts.util;
22  
23  import org.apache.commons.logging.Log;
24  import org.apache.commons.logging.LogFactory;
25  import org.apache.struts.config.MessageResourcesConfig;
26  
27  import java.io.Serializable;
28  
29  /**
30   * Factory for <code>MessageResources</code> instances.  The general usage
31   * pattern for this class is:
32   *
33   * <ul>
34   *
35   * <li>Call <code>MessageResourcesFactory().createFactory()</code> to retrieve
36   * a <code>MessageResourcesFactory</code> instance.</li> <li>Set properties as
37   * required to configure this factory instance to create
38   * <code>MessageResources</code> instances with desired characteristics.</li>
39   *
40   * <li>Call the <code>createResources()</code> method of the factory to
41   * retrieve a newly instantiated <code>MessageResources</code> instance.</li>
42   *
43   * </ul>
44   *
45   * @version $Rev: 471754 $ $Date: 2005-08-29 23:57:50 -0400 (Mon, 29 Aug 2005)
46   *          $
47   */
48  public abstract class MessageResourcesFactory implements Serializable {
49      // ------------------------------------------------------ Static Properties
50  
51      /**
52       * The Java class to be used for <code>MessageResourcesFactory</code>
53       * instances.
54       */
55      protected static transient Class clazz = null;
56  
57      /**
58       * Commons Logging instance.
59       */
60      private static Log LOG = LogFactory.getLog(MessageResourcesFactory.class);
61  
62      /**
63       * The fully qualified class name to be used for <code>MessageResourcesFactory</code>
64       * instances.
65       */
66      protected static String factoryClass =
67          "org.apache.struts.util.PropertyMessageResourcesFactory";
68  
69      // ---------------------------------------------------- Instance Properties
70  
71      /**
72       * Configuration information for Message Resources.
73       */
74      protected MessageResourcesConfig config;
75  
76      /**
77       * The "return null" property value to which newly created
78       * MessageResourcess should be initialized.
79       */
80      protected boolean returnNull = true;
81  
82      /**
83       * Set the configuration information for Message Resources.
84       *
85       * @since Struts 1.2.8
86       */
87      public MessageResourcesConfig getConfig() {
88          return config;
89      }
90  
91      /**
92       * Return the configuration information for Message Resources.
93       *
94       * @since Struts 1.2.8
95       */
96      public void setConfig(MessageResourcesConfig config) {
97          this.config = config;
98      }
99  
100     /**
101      * Get default value of the "returnNull" property used to initialize newly
102      * created MessageResourcess.
103      *
104      * @return default value of the "returnNull" property newly created
105      *         MessageResourcess are initialized to.
106      */
107     public boolean getReturnNull() {
108         return (this.returnNull);
109     }
110 
111     /**
112      * Set the default value of the "returnNull" property newly created
113      * MessageResourcess are initialized to.
114      *
115      * @param returnNull default value of the "returnNull" MessageResourcess
116      *                   are initialized to.
117      */
118     public void setReturnNull(boolean returnNull) {
119         this.returnNull = returnNull;
120     }
121 
122     // --------------------------------------------------------- Public Methods
123 
124     /**
125      * Create and return a newly instansiated <code>MessageResources</code>.
126      * This method must be implemented by concrete subclasses.
127      *
128      * @param config Configuration parameter(s) for the requested bundle
129      */
130     public abstract MessageResources createResources(String config);
131 
132     /**
133      * The fully qualified class name that is used for <code>MessageResourcesFactory</code>
134      * instances.
135      *
136      * @return class name that is used for <code>MessageResourcesFactory</code>
137      *         instances
138      */
139     public static String getFactoryClass() {
140         return (MessageResourcesFactory.factoryClass);
141     }
142 
143     /**
144      * Set the fully qualified class name that is used for
145      * <code>MessageResourcesFactory</code> instances.
146      *
147      * @param factoryClass name that is used for <code>MessageResourcesFactory</code>
148      *                     instances
149      */
150     public static void setFactoryClass(String factoryClass) {
151         MessageResourcesFactory.factoryClass = factoryClass;
152         MessageResourcesFactory.clazz = null;
153     }
154 
155     // --------------------------------------------------------- Static Methods
156 
157     /**
158      * Create and return a <code>MessageResourcesFactory</code> instance of
159      * the appropriate class, which can be used to create customized
160      * <code>MessageResources</code> instances.  If no such factory can be
161      * created, return <code>null</code> instead.
162      */
163     public static MessageResourcesFactory createFactory() {
164         // Construct a new instance of the specified factory class
165         try {
166             if (clazz == null) {
167                 clazz = RequestUtils.applicationClass(factoryClass);
168             }
169 
170             MessageResourcesFactory factory =
171                 (MessageResourcesFactory) clazz.newInstance();
172 
173             return (factory);
174         } catch (Throwable t) {
175             LOG.error("MessageResourcesFactory.createFactory", t);
176 
177             return (null);
178         }
179     }
180 }