001/*
002 * Copyright 2002-2012 the original author or authors.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *      https://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package org.springframework.beans.factory.parsing;
018
019import org.springframework.beans.BeanMetadataElement;
020import org.springframework.beans.factory.config.BeanDefinition;
021import org.springframework.beans.factory.config.BeanReference;
022
023/**
024 * Interface that describes the logical view of a set of {@link BeanDefinition BeanDefinitions}
025 * and {@link BeanReference BeanReferences} as presented in some configuration context.
026 *
027 * <p>With the introduction of {@link org.springframework.beans.factory.xml.NamespaceHandler pluggable custom XML tags},
028 * it is now possible for a single logical configuration entity, in this case an XML tag, to
029 * create multiple {@link BeanDefinition BeanDefinitions} and {@link BeanReference RuntimeBeanReferences}
030 * in order to provide more succinct configuration and greater convenience to end users. As such, it can
031 * no longer be assumed that each configuration entity (e.g. XML tag) maps to one {@link BeanDefinition}.
032 * For tool vendors and other users who wish to present visualization or support for configuring Spring
033 * applications it is important that there is some mechanism in place to tie the {@link BeanDefinition BeanDefinitions}
034 * in the {@link org.springframework.beans.factory.BeanFactory} back to the configuration data in a way
035 * that has concrete meaning to the end user. As such, {@link org.springframework.beans.factory.xml.NamespaceHandler}
036 * implementations are able to publish events in the form of a {@code ComponentDefinition} for each
037 * logical entity being configured. Third parties can then {@link ReaderEventListener subscribe to these events},
038 * allowing for a user-centric view of the bean metadata.
039 *
040 * <p>Each {@code ComponentDefinition} has a {@link #getSource source object} which is configuration-specific.
041 * In the case of XML-based configuration this is typically the {@link org.w3c.dom.Node} which contains the user
042 * supplied configuration information. In addition to this, each {@link BeanDefinition} enclosed in a
043 * {@code ComponentDefinition} has its own {@link BeanDefinition#getSource() source object} which may point
044 * to a different, more specific, set of configuration data. Beyond this, individual pieces of bean metadata such
045 * as the {@link org.springframework.beans.PropertyValue PropertyValues} may also have a source object giving an
046 * even greater level of detail. Source object extraction is handled through the
047 * {@link SourceExtractor} which can be customized as required.
048 *
049 * <p>Whilst direct access to important {@link BeanReference BeanReferences} is provided through
050 * {@link #getBeanReferences}, tools may wish to inspect all {@link BeanDefinition BeanDefinitions} to gather
051 * the full set of {@link BeanReference BeanReferences}. Implementations are required to provide
052 * all {@link BeanReference BeanReferences} that are required to validate the configuration of the
053 * overall logical entity as well as those required to provide full user visualisation of the configuration.
054 * It is expected that certain {@link BeanReference BeanReferences} will not be important to
055 * validation or to the user view of the configuration and as such these may be omitted. A tool may wish to
056 * display any additional {@link BeanReference BeanReferences} sourced through the supplied
057 * {@link BeanDefinition BeanDefinitions} but this is not considered to be a typical case.
058 *
059 * <p>Tools can determine the important of contained {@link BeanDefinition BeanDefinitions} by checking the
060 * {@link BeanDefinition#getRole role identifier}. The role is essentially a hint to the tool as to how
061 * important the configuration provider believes a {@link BeanDefinition} is to the end user. It is expected
062 * that tools will <strong>not</strong> display all {@link BeanDefinition BeanDefinitions} for a given
063 * {@code ComponentDefinition} choosing instead to filter based on the role. Tools may choose to make
064 * this filtering user configurable. Particular notice should be given to the
065 * {@link BeanDefinition#ROLE_INFRASTRUCTURE INFRASTRUCTURE role identifier}. {@link BeanDefinition BeanDefinitions}
066 * classified with this role are completely unimportant to the end user and are required only for
067 * internal implementation reasons.
068 *
069 * @author Rob Harrop
070 * @author Juergen Hoeller
071 * @since 2.0
072 * @see AbstractComponentDefinition
073 * @see CompositeComponentDefinition
074 * @see BeanComponentDefinition
075 * @see ReaderEventListener#componentRegistered(ComponentDefinition)
076 */
077public interface ComponentDefinition extends BeanMetadataElement {
078
079        /**
080         * Get the user-visible name of this {@code ComponentDefinition}.
081         * <p>This should link back directly to the corresponding configuration data
082         * for this component in a given context.
083         */
084        String getName();
085
086        /**
087         * Return a friendly description of the described component.
088         * <p>Implementations are encouraged to return the same value from
089         * {@code toString()}.
090         */
091        String getDescription();
092
093        /**
094         * Return the {@link BeanDefinition BeanDefinitions} that were registered
095         * to form this {@code ComponentDefinition}.
096         * <p>It should be noted that a {@code ComponentDefinition} may well be related with
097         * other {@link BeanDefinition BeanDefinitions} via {@link BeanReference references},
098         * however these are <strong>not</strong> included as they may be not available immediately.
099         * Important {@link BeanReference BeanReferences} are available from {@link #getBeanReferences()}.
100         * @return the array of BeanDefinitions, or an empty array if none
101         */
102        BeanDefinition[] getBeanDefinitions();
103
104        /**
105         * Return the {@link BeanDefinition BeanDefinitions} that represent all relevant
106         * inner beans within this component.
107         * <p>Other inner beans may exist within the associated {@link BeanDefinition BeanDefinitions},
108         * however these are not considered to be needed for validation or for user visualization.
109         * @return the array of BeanDefinitions, or an empty array if none
110         */
111        BeanDefinition[] getInnerBeanDefinitions();
112
113        /**
114         * Return the set of {@link BeanReference BeanReferences} that are considered
115         * to be important to this {@code ComponentDefinition}.
116         * <p>Other {@link BeanReference BeanReferences} may exist within the associated
117         * {@link BeanDefinition BeanDefinitions}, however these are not considered
118         * to be needed for validation or for user visualization.
119         * @return the array of BeanReferences, or an empty array if none
120         */
121        BeanReference[] getBeanReferences();
122
123}