    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 * @author <a
    045 * href="http://commons.apache.org/configuration/team-list.html">Commons
    046 * Configuration team</a>
    047 */
    048public interface BeanDeclaration
    049{
    050    /**
    051     * Returns the name of the {@code BeanFactory} that should be used
    052     * for creating the bean instance. This can be <b>null</b>, then a default
    053     * factory will be used.
    054     *
    055     * @return the name of the bean factory
    056     */
    057    String getBeanFactoryName();
    058
    059    /**
    060     * Here an arbitrary object can be returned that will be passed to the bean
    061     * factory. Its meaning is not further specified. The purpose of this
    062     * additional parameter is to support a further configuration of the bean
    063     * factory that can be placed directly at the bean declaration.
    064     *
    065     * @return a parameter for the bean factory
    066     */
    067    Object getBeanFactoryParameter();
    068
    069    /**
    070     * Returns the name of the bean class, from which an instance is to be
    071     * created. This value must be defined unless a default class is provided
    072     * for the bean creation operation.
    073     *
    074     * @return the name of the bean class
    075     */
    076    String getBeanClassName();
    077
    078    /**
    079     * Returns a map with properties that should be initialized on the newly
    080     * created bean. The map's keys are the names of the properties; the
    081     * corresponding values are the properties' values. The return value can be
    082     * <b>null</b> if no properties should be set.
    083     *
    084     * @return a map with properties to be initialized
    085     */
    086    Map<String, Object> getBeanProperties();
    087
    088    /**
    089     * Returns a map with declarations for beans that should be set as
    090     * properties of the newly created bean. This allows for complex
    091     * initialization scenarios: a bean for a bean that contains complex
    092     * properties (e.g. other beans) can have nested declarations for defining
    093     * these complex properties. The returned map's key are the names of the
    094     * properties to initialize. The values are either {@code BeanDeclaration}
    095     * implementations or collections thereof. They will be treated like this
    096     * declaration (in a recursive manner), and the resulting beans are
    097     * assigned to the corresponding properties.
    098     *
    099     * @return a map with nested bean declarations
    100     */
    101    Map<String, Object> getNestedBeanDeclarations();
    102
    103    /**
    104     * Returns a collection with constructor arguments. This data is used to
    105     * determine the constructor of the bean class to be invoked. The values of
    106     * the arguments are passed to the constructor. An implementation can return
    107     * <b>null</b> or an empty collection; then the standard constructor of the
    108     * bean class is called.
    109     *
    110     * @return a collection with the arguments to be passed to the bean class's
    111     *         constructor
    112     */
    113    Collection<ConstructorArg> getConstructorArgs();
    114}