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