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 */ 017package org.apache.commons.configuration2.beanutils; 018 019/** 020 * <p> 021 * Definition of an interface for bean factories. 022 * </p> 023 * <p> 024 * Beans defined in configuration files are not directly created, but by so 025 * called <em>bean factories</em>. This additional level of indirection 026 * provides for high flexibility in the creation process. For instance one 027 * implementation of this interface could be very simple and create a new 028 * instance of the specified class for each invocation. A different 029 * implementation could cache already created beans and ensure that always the 030 * same bean of the given class will be returned - this would be an easy mean 031 * for creating singleton objects. 032 * </p> 033 * <p> 034 * The interface itself is quite simple. There is a single method for creating a 035 * bean of a given class. All necessary parameters are obtained from a 036 * passed in {@link BeanCreationContext} object. It is also possible 037 * (but optional) for a bean factory to declare the default class of the bean it 038 * creates. Then it is not necessary to specify a bean class in the bean 039 * declaration. 040 * </p> 041 * 042 * @since 1.3 043 */ 044public interface BeanFactory 045{ 046 /** 047 * Returns a bean instance for the given context object. All information 048 * about the bean to be created are contained in the provided 049 * {@code BeanCreationContext} object. This includes a 050 * {@link BeanDeclaration} defining the properties of the bean. It is up to 051 * a concrete implementation how the bean is created and initialized. 052 * 053 * @param bcc the context object for the bean to be created 054 * @return the new bean instance (should not be <b>null</b>) 055 * @throws Exception if an error occurs (the helper classes for creating 056 * beans will catch this generic exception and wrap it in a 057 * configuration exception) 058 */ 059 Object createBean(BeanCreationContext bcc) throws Exception; 060 061 /** 062 * Returns the default bean class of this bean factory. If an implementation 063 * here returns a non <b>null</b> value, bean declarations using this 064 * factory do not need to provide the name of the bean class. In such a case 065 * an instance of the default class will be created. 066 * 067 * @return the default class of this factory or <b>null</b> if there is 068 * none 069 */ 070 Class<?> getDefaultBeanClass(); 071}