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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} interface.
22   * </p>
23   * <p>
24   * This class creates beans of arbitrary types using reflection. Each time the
25   * {@code createBean()} 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 {@link BeanHelper} class. This means that if not bean
31   * factory is specified in a {@link BeanDeclaration}, this
32   * default instance will be used.
33   * </p>
34   *
35   * @since 1.3
36   * @author <a
37   * href="http://commons.apache.org/configuration/team-list.html">Commons
38   * Configuration team</a>
39   * @version $Id: DefaultBeanFactory.java 1208758 2011-11-30 20:38:59Z oheger $
40   */
41  public class DefaultBeanFactory implements BeanFactory
42  {
43      /** Stores the default instance of this class. */
44      public static final DefaultBeanFactory INSTANCE = new DefaultBeanFactory();
45  
46      /**
47       * Creates a new bean instance. This implementation delegates to the
48       * protected methods {@code createBeanInstance()} and
49       * {@code initBeanInstance()} for creating and initializing the bean.
50       * This makes it easier for derived classes that need to change specific
51       * functionality of the base class.
52       *
53       * @param beanClass the class of the bean, from which an instance is to be
54       * created
55       * @param data the bean declaration object
56       * @param parameter an additional parameter (ignored by this implementation)
57       * @return the new bean instance
58       * @throws Exception if an error occurs
59       */
60      public Object createBean(Class<?> beanClass, BeanDeclaration data,
61              Object parameter) throws Exception
62      {
63          Object result = createBeanInstance(beanClass, data);
64          initBeanInstance(result, data);
65          return result;
66      }
67  
68      /**
69       * Returns the default bean class used by this factory. This is always
70       * <b>null</b> for this implementation.
71       *
72       * @return the default bean class
73       */
74      public Class<?> getDefaultBeanClass()
75      {
76          return null;
77      }
78  
79      /**
80       * Creates the bean instance. This method is called by
81       * {@code createBean()}. It uses reflection to create a new instance
82       * of the specified class.
83       *
84       * @param beanClass the class of the bean to be created
85       * @param data the bean declaration
86       * @return the new bean instance
87       * @throws Exception if an error occurs
88       */
89      protected Object createBeanInstance(Class<?> beanClass, BeanDeclaration data)
90              throws Exception
91      {
92          return beanClass.newInstance();
93      }
94  
95      /**
96       * Initializes the newly created bean instance. This method is called by
97       * {@code createBean()}. It calls the
98       * {@link BeanHelper#initBean(Object, BeanDeclaration) initBean()}
99       * of {@link BeanHelper} for performing the initialization.
100      *
101      * @param bean the newly created bean instance
102      * @param data the bean declaration object
103      * @throws Exception if an error occurs
104      */
105     protected void initBeanInstance(Object bean, BeanDeclaration data)
106             throws Exception
107     {
108         BeanHelper.initBean(bean, data);
109     }
110 }