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     */
017    package org.apache.commons.configuration.beanutils;
018    
019    import java.util.Map;
020    
021    /**
022     * <p>
023     * Definition of an interface for declaring a bean in a configuration file.
024     * </p>
025     * <p>
026     * Commons Configurations allows to define beans (i.e. simple Java objects) in
027     * configuration files, which can be created at runtime. This is especially
028     * useful if you program against interfaces and want to define the concrete
029     * implementation class is a configuration file.
030     * </p>
031     * <p>
032     * This interface defines methods for retrieving all information about a bean
033     * that should be created from a configuration file, e.g. the bean's properties
034     * or the factory to use for creating the instance. With different
035     * implementations different &quot;layouts&quot; of bean declarations can be
036     * supported. For instance if an XML configuration file is used, all features of
037     * XML (e.g. attributes, nested elements) can be used to define the bean. In a
038     * properties file the declaration format is more limited. The purpose of this
039     * interface is to abstract from the concrete declaration format.
040     * </p>
041     *
042     * @since 1.3
043     * @author <a
044     * href="http://commons.apache.org/configuration/team-list.html">Commons
045     * Configuration team</a>
046     * @version $Id: BeanDeclaration.java 1208756 2011-11-30 20:37:32Z oheger $
047     */
048    public 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    }