    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}