FinderFromDfltResource


1   /* $Id: FinderFromDfltResource.java 179714 2005-06-03 03:53:39Z skitching $
2    *
3    * Copyright 2004 The Apache Software Foundation.
4    * 
5    * Licensed under the Apache License, Version 2.0 (the "License");
6    * you may not use this file except in compliance with the License.
7    * You may obtain a copy of the License at
8    * 
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   * 
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */ 
17   
18  package org.apache.commons.digester.plugins.strategies;
19  
20  import java.io.InputStream  ;
21  import java.util.Properties  ;
22  
23  import org.apache.commons.digester.Digester;
24  import org.apache.commons.digester.plugins.RuleFinder;
25  import org.apache.commons.digester.plugins.RuleLoader;
26  import org.apache.commons.digester.plugins.PluginException;
27  
28  /**
29   * A rule-finding algorithm which looks for a resource file in the classpath
30   * whose name is derived from the plugin class name plus a specified suffix.
31   * <p>
32   * If the resource-file is found, then it is expected to define a set of
33   * Digester rules in xmlrules format.
34   *
35   * @since 1.6
36   */
37  
38  public class FinderFromDfltResource extends RuleFinder {
39      public static String   DFLT_RESOURCE_SUFFIX = "RuleInfo.xml";
40  
41      private String   resourceSuffix;
42      
43      /** See {@link #findLoader}. */
44      public FinderFromDfltResource() { 
45          this(DFLT_RESOURCE_SUFFIX);
46      }
47  
48      /**
49       * Create a rule-finder which can load an xmlrules file, cache
50       * the rules away, and later add them as a plugin's custom rules
51       * when that plugin is referenced.
52       *
53       * @param resourceSuffix must be non-null.
54       */
55      public FinderFromDfltResource(String   resourceSuffix) { 
56          this.resourceSuffix = resourceSuffix;
57      }
58      
59      /**
60       * If there exists a resource file whose name is equal to the plugin
61       * class name + the suffix specified in the constructor, then
62       * load that file, run it through the xmlrules module and return an object 
63       * encapsulating those rules.
64       * <p>
65       * If there is no such resource file, then just return null.
66       * <p>
67       * The returned object (when non-null) will add the selected rules to
68       * the digester whenever its addRules method is invoked.
69       */
70      public RuleLoader findLoader(Digester d, Class   pluginClass, Properties   p)
71                          throws PluginException {
72  
73          String   resourceName = 
74              pluginClass.getName().replace('.', '/') 
75                      + resourceSuffix;
76              
77          InputStream   is = 
78              pluginClass.getClassLoader().getResourceAsStream(
79                  resourceName);
80  
81          if (is == null) {
82              // ok, no such resource
83              return null;
84          }
85  
86          return FinderFromResource.loadRules(d, pluginClass, is, resourceName);
87      }
88  }
89  
90
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