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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  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  package org.apache.commons.configuration.beanutils;
18  
19  /***
20   * <p>
21   * The default implementation of the <code>BeanFactory</code> interface.
22   * </p>
23   * <p>
24   * This class creates beans of arbitrary types using reflection. Each time the
25   * <code>createBean()</code> method is invoked, a new bean instance is
26   * created. A default bean class is not supported.
27   * </p>
28   * <p>
29   * An instance of this factory class will be set as the default bean factory for
30   * the <code>{@link BeanHelper}</code> class. This means that if not bean
31   * factory is specified in a <code>{@link BeanDeclaration}</code>, this
32   * default instance will be used.
33   * </p>
34   *
35   * @since 1.3
36   * @author Oliver Heger
37   * @version $Id: DefaultBeanFactory.java 439648 2006-09-02 20:42:10Z oheger $
38   */
39  public class DefaultBeanFactory implements BeanFactory
40  {
41      /*** Stores the default instance of this class. */
42      public static final DefaultBeanFactory INSTANCE = new DefaultBeanFactory();
43  
44      /***
45       * Creates a new bean instance. This implementation delegates to the
46       * protected methods <code>createBeanInstance()</code> and
47       * <code>initBeanInstance()</code> for creating and initializing the bean.
48       * This makes it easier for derived classes that need to change specific
49       * functionality of the base class.
50       *
51       * @param beanClass the class of the bean, from which an instance is to be
52       * created
53       * @param data the bean declaration object
54       * @param parameter an additional parameter (ignored by this implementation)
55       * @return the new bean instance
56       * @throws Exception if an error occurs
57       */
58      public Object createBean(Class beanClass, BeanDeclaration data,
59              Object parameter) throws Exception
60      {
61          Object result = createBeanInstance(beanClass, data);
62          initBeanInstance(result, data);
63          return result;
64      }
65  
66      /***
67       * Returns the default bean class used by this factory. This is always
68       * <b>null</b> for this implementation.
69       *
70       * @return the default bean class
71       */
72      public Class getDefaultBeanClass()
73      {
74          return null;
75      }
76  
77      /***
78       * Creates the bean instance. This method is called by
79       * <code>createBean()</code>. It uses reflection to create a new instance
80       * of the specified class.
81       *
82       * @param beanClass the class of the bean to be created
83       * @param data the bean declaration
84       * @return the new bean instance
85       * @throws Exception if an error occurs
86       */
87      protected Object createBeanInstance(Class beanClass, BeanDeclaration data)
88              throws Exception
89      {
90          return beanClass.newInstance();
91      }
92  
93      /***
94       * Initializes the newly created bean instance. This method is called by
95       * <code>createBean()</code>. It calls the
96       * <code>{@link BeanHelper#initBean(Object, BeanDeclaration) initBean()}</code>
97       * of <code>{@link BeanHelper}</code> for performing the initialization.
98       *
99       * @param bean the newly created bean instance
100      * @param data the bean declaration object
101      * @throws Exception if an error occurs
102      */
103     protected void initBeanInstance(Object bean, BeanDeclaration data)
104             throws Exception
105     {
106         BeanHelper.initBean(bean, data);
107     }
108 }