001    /*
002     * Licensed to the Apache Software Foundation (ASF) under one or more
003     * contributor license agreements.  See the NOTICE file distributed with
004     * this work for additional information regarding copyright ownership.
005     * The ASF licenses this file to You under the Apache License, Version 2.0
006     * (the "License"); you may not use this file except in compliance with
007     * the License.  You may obtain a copy of the License at
008     *
009     *     http://www.apache.org/licenses/LICENSE-2.0
010     *
011     * Unless required by applicable law or agreed to in writing, software
012     * distributed under the License is distributed on an "AS IS" BASIS,
013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     * See the License for the specific language governing permissions and
015     * limitations under the License.
016     */
017    package org.apache.commons.configuration.beanutils;
018    
019    /**
020     * <p>
021     * The default implementation of the <code>BeanFactory</code> interface.
022     * </p>
023     * <p>
024     * This class creates beans of arbitrary types using reflection. Each time the
025     * <code>createBean()</code> method is invoked, a new bean instance is
026     * created. A default bean class is not supported.
027     * </p>
028     * <p>
029     * An instance of this factory class will be set as the default bean factory for
030     * the <code>{@link BeanHelper}</code> class. This means that if not bean
031     * factory is specified in a <code>{@link BeanDeclaration}</code>, this
032     * default instance will be used.
033     * </p>
034     *
035     * @since 1.3
036     * @author Oliver Heger
037     * @version $Id: DefaultBeanFactory.java 439648 2006-09-02 20:42:10Z oheger $
038     */
039    public class DefaultBeanFactory implements BeanFactory
040    {
041        /** Stores the default instance of this class. */
042        public static final DefaultBeanFactory INSTANCE = new DefaultBeanFactory();
043    
044        /**
045         * Creates a new bean instance. This implementation delegates to the
046         * protected methods <code>createBeanInstance()</code> and
047         * <code>initBeanInstance()</code> for creating and initializing the bean.
048         * This makes it easier for derived classes that need to change specific
049         * functionality of the base class.
050         *
051         * @param beanClass the class of the bean, from which an instance is to be
052         * created
053         * @param data the bean declaration object
054         * @param parameter an additional parameter (ignored by this implementation)
055         * @return the new bean instance
056         * @throws Exception if an error occurs
057         */
058        public Object createBean(Class beanClass, BeanDeclaration data,
059                Object parameter) throws Exception
060        {
061            Object result = createBeanInstance(beanClass, data);
062            initBeanInstance(result, data);
063            return result;
064        }
065    
066        /**
067         * Returns the default bean class used by this factory. This is always
068         * <b>null</b> for this implementation.
069         *
070         * @return the default bean class
071         */
072        public Class getDefaultBeanClass()
073        {
074            return null;
075        }
076    
077        /**
078         * Creates the bean instance. This method is called by
079         * <code>createBean()</code>. It uses reflection to create a new instance
080         * of the specified class.
081         *
082         * @param beanClass the class of the bean to be created
083         * @param data the bean declaration
084         * @return the new bean instance
085         * @throws Exception if an error occurs
086         */
087        protected Object createBeanInstance(Class beanClass, BeanDeclaration data)
088                throws Exception
089        {
090            return beanClass.newInstance();
091        }
092    
093        /**
094         * Initializes the newly created bean instance. This method is called by
095         * <code>createBean()</code>. It calls the
096         * <code>{@link BeanHelper#initBean(Object, BeanDeclaration) initBean()}</code>
097         * of <code>{@link BeanHelper}</code> for performing the initialization.
098         *
099         * @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    }