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 * @version $Id: BeanDeclaration.java 1624601 2014-09-12 18:04:36Z oheger $
048 */
049public interface BeanDeclaration
050{
051    /**
052     * Returns the name of the {@code BeanFactory} that should be used
053     * for creating the bean instance. This can be <b>null</b>, then a default
054     * factory will be used.
055     *
056     * @return the name of the bean factory
057     */
058    String getBeanFactoryName();
059
060    /**
061     * Here an arbitrary object can be returned that will be passed to the bean
062     * factory. Its meaning is not further specified. The purpose of this
063     * additional parameter is to support a further configuration of the bean
064     * factory that can be placed directly at the bean declaration.
065     *
066     * @return a parameter for the bean factory
067     */
068    Object getBeanFactoryParameter();
069
070    /**
071     * Returns the name of the bean class, from which an instance is to be
072     * created. This value must be defined unless a default class is provided
073     * for the bean creation operation.
074     *
075     * @return the name of the bean class
076     */
077    String getBeanClassName();
078
079    /**
080     * Returns a map with properties that should be initialized on the newly
081     * created bean. The map's keys are the names of the properties; the
082     * corresponding values are the properties' values. The return value can be
083     * <b>null</b> if no properties should be set.
084     *
085     * @return a map with properties to be initialized
086     */
087    Map<String, Object> getBeanProperties();
088
089    /**
090     * Returns a map with declarations for beans that should be set as
091     * properties of the newly created bean. This allows for complex
092     * initialization scenarios: a bean for a bean that contains complex
093     * properties (e.g. other beans) can have nested declarations for defining
094     * these complex properties. The returned map's key are the names of the
095     * properties to initialize. The values are either {@code BeanDeclaration}
096     * implementations or collections thereof. They will be treated like this
097     * declaration (in a recursive manner), and the resulting beans are
098     * assigned to the corresponding properties.
099     *
100     * @return a map with nested bean declarations
101     */
102    Map<String, Object> getNestedBeanDeclarations();
103
104    /**
105     * Returns a collection with constructor arguments. This data is used to
106     * determine the constructor of the bean class to be invoked. The values of
107     * the arguments are passed to the constructor. An implementation can return
108     * <b>null</b> or an empty collection; then the standard constructor of the
109     * bean class is called.
110     *
111     * @return a collection with the arguments to be passed to the bean class's
112     *         constructor
113     */
114    Collection<ConstructorArg> getConstructorArgs();
115}