    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
    019import java.util.Collection;
    020import java.util.Map;
    021
    022/**
    023 * <p>
    024 * Definition of an interface for declaring a bean in a configuration file.
    025 * </p>
    026 * <p>
    027 * Commons Configurations allows to define beans (i.e. simple Java objects) in
    028 * configuration files, which can be created at runtime. This is especially
    029 * useful if you program against interfaces and want to define the concrete
    030 * implementation class is a configuration file.
    031 * </p>
    032 * <p>
    033 * This interface defines methods for retrieving all information about a bean
    034 * that should be created from a configuration file, e.g. the bean's properties
    035 * or the factory to use for creating the instance. With different
    036 * implementations different &quot;layouts&quot; of bean declarations can be
    037 * supported. For instance if an XML configuration file is used, all features of
    038 * XML (e.g. attributes, nested elements) can be used to define the bean. In a
    039 * properties file the declaration format is more limited. The purpose of this
    040 * interface is to abstract from the concrete declaration format.
    041 * </p>
    042 *
    043 * @since 1.3
    044 */
    045public interface BeanDeclaration
    046{
    047    /**
    048     * Returns the name of the {@code BeanFactory} that should be used
    049     * for creating the bean instance. This can be <b>null</b>, then a default
    050     * factory will be used.
    051     *
    052     * @return the name of the bean factory
    053     */
    054    String getBeanFactoryName();
    055
    056    /**
    057     * Here an arbitrary object can be returned that will be passed to the bean
    058     * factory. Its meaning is not further specified. The purpose of this
    059     * additional parameter is to support a further configuration of the bean
    060     * factory that can be placed directly at the bean declaration.
    061     *
    062     * @return a parameter for the bean factory
    063     */
    064    Object getBeanFactoryParameter();
    065
    066    /**
    067     * Returns the name of the bean class, from which an instance is to be
    068     * created. This value must be defined unless a default class is provided
    069     * for the bean creation operation.
    070     *
    071     * @return the name of the bean class
    072     */
    073    String getBeanClassName();
    074
    075    /**
    076     * Returns a map with properties that should be initialized on the newly
    077     * created bean. The map's keys are the names of the properties; the
    078     * corresponding values are the properties' values. The return value can be
    079     * <b>null</b> if no properties should be set.
    080     *
    081     * @return a map with properties to be initialized
    082     */
    083    Map<String, Object> getBeanProperties();
    084
    085    /**
    086     * Returns a map with declarations for beans that should be set as
    087     * properties of the newly created bean. This allows for complex
    088     * initialization scenarios: a bean for a bean that contains complex
    089     * properties (e.g. other beans) can have nested declarations for defining
    090     * these complex properties. The returned map's key are the names of the
    091     * properties to initialize. The values are either {@code BeanDeclaration}
    092     * implementations or collections thereof. They will be treated like this
    093     * declaration (in a recursive manner), and the resulting beans are
    094     * assigned to the corresponding properties.
    095     *
    096     * @return a map with nested bean declarations
    097     */
    098    Map<String, Object> getNestedBeanDeclarations();
    099
    100    /**
    101     * Returns a collection with constructor arguments. This data is used to
    102     * determine the constructor of the bean class to be invoked. The values of
    103     * the arguments are passed to the constructor. An implementation can return
    104     * <b>null</b> or an empty collection; then the standard constructor of the
    105     * bean class is called.
    106     *
    107     * @return a collection with the arguments to be passed to the bean class's
    108     *         constructor
    109     */
    110    Collection<ConstructorArg> getConstructorArgs();
    111}