View Javadoc

1   /*
2    * Copyright 2002-2004 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  package org.apache.commons.clazz;
17  
18  import java.util.HashSet;
19  
20  /***
21   * Constructs/loads Clazzes.
22   * 
23   * @author <a href="mailto:dmitri@apache.org">Dmitri Plotnikov</a>
24   * @version $Id: ClazzLoader.java,v 1.7 2004/02/19 23:58:37 scolebourne Exp $
25   */
26  public abstract class ClazzLoader {
27      private ModelClazzLoader modelClazzLoader;
28  
29      /***
30       * ClazzLoaders are grouped into models.
31       */
32      public ClazzLoader(ModelClazzLoader modelClazzLoader) {
33          this.modelClazzLoader = modelClazzLoader;
34      }
35  
36      /***
37       * Returns the model clazz loader for this clazz loader.
38       */
39      public ModelClazzLoader getModelClazzLoader() {
40          return modelClazzLoader;
41      }
42  
43      /***
44       * Returns the name of the model this clazz loader belongs to.
45       */
46      public String getModel() {
47          return getModelClazzLoader().getModel();
48      }
49  
50      /***
51       * Given a Clazz name, returns the corresponding Clazz. Does not
52       * cache clazzes, that's the job of CachingGroupClazzLoader.  Return null if
53       * there is no Clazz for this name.
54       * <p>
55       * Note that we use canonical class names for primitive types and arrays, 
56       * e.g. "byte", "byte[]", "boolean[][]", "java.lang.String[]".
57       */
58      public abstract Clazz getClazzForName(String name);
59  
60      /***
61       * Returns true iff this loader has or can construct a Clazz for the
62       * supplied instance.
63       */
64      public abstract boolean isMember(Object instance);
65  
66      /***
67       * Returns the Clazz for the supplied instance.  Returns <code>null</code>
68       * if it cannot produce such a Clazz.
69       */
70      public Clazz getClazz(Object instance) {
71          if (instance == null) {
72              return null;
73          }
74  
75          String name = getClazzName(instance);
76          if (name == null) {
77              return null;
78          }
79          return getClazzForName(name);
80      }
81  
82      /***
83       * Returns the clazz name for the supplied instance. Returns
84       * <code>null</code> if it cannot produce a clazz name for the instance.
85       */
86      public abstract String getClazzName(Object instance);
87  
88      /***
89       * Defines a new Clazz with the supplied name.  If it cannot define a
90       * clazz of the supplied type or if it cannot define clazzes at all, returns
91       * null.
92       * 
93       * @param name the name of the clazz, should be unique within the scope of
94       * the top-level ClazzLoader
95       * @param clazzClass the Class of the Clazz that this method needs to
96       * produce.
97       * @param instanceClass the Class of the instances the new Clazz will be
98       * able to create using the <code>newInstance()</code> method.
99       * 
100      * @return Clazz
101      */
102     public abstract Clazz defineClazz(
103         String name,
104         Class clazzClass,
105         Class instanceClass);
106 
107     private HashSet loggingEnabledClasses = new HashSet();
108 
109     /***
110      * Enable diagnistic logging for the specified class.
111      */
112     public void enableLogging(String className) {
113         loggingEnabledClasses.add(className);
114     }
115 
116     public boolean isLoggingEnabled(String className) {
117         return loggingEnabledClasses.contains(className);
118     }
119 
120 }