/*
 * Copyright 2002-2019 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.beans.factory;

import java.lang.annotation.Annotation;
import java.util.Map;

import org.springframework.beans.BeansException;
import org.springframework.core.ResolvableType;
import org.springframework.lang.Nullable;

/**
 * Extension of the {@link BeanFactory} interface to be implemented by bean factories
 * that can enumerate all their bean instances, rather than attempting bean lookup
 * by name one by one as requested by clients. BeanFactory implementations that
 * preload all their bean definitions (such as XML-based factories) may implement
 * this interface.
 *
 * <p>If this is a {@link HierarchicalBeanFactory}, the return values will <i>not</i>
 * take any BeanFactory hierarchy into account, but will relate only to the beans
 * defined in the current factory. Use the {@link BeanFactoryUtils} helper class
 * to consider beans in ancestor factories too.
 *
 * <p>The methods in this interface will just respect bean definitions of this factory.
 * They will ignore any singleton beans that have been registered by other means like
 * {@link org.springframework.beans.factory.config.ConfigurableBeanFactory}'s
 * {@code registerSingleton} method, with the exception of
 * {@code getBeanNamesOfType} and {@code getBeansOfType} which will check
 * such manually registered singletons too. Of course, BeanFactory's {@code getBean}
 * does allow transparent access to such special beans as well. However, in typical
 * scenarios, all beans will be defined by external bean definitions anyway, so most
 * applications don't need to worry about this differentiation.
 *
 * <p><b>NOTE:</b> With the exception of {@code getBeanDefinitionCount}
 * and {@code containsBeanDefinition}, the methods in this interface
 * are not designed for frequent invocation. Implementations may be slow.
 *
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @since 16 April 2001
 * @see HierarchicalBeanFactory
 * @see BeanFactoryUtils
 */
public interface ListableBeanFactory extends BeanFactory {

	/**
	 * Check if this bean factory contains a bean definition with the given name.
	 * <p>Does not consider any hierarchy this factory may participate in,
	 * and ignores any singleton beans that have been registered by
	 * other means than bean definitions.
	 * @param beanName the name of the bean to look for
	 * @return if this bean factory contains a bean definition with the given name
	 * @see #containsBean
	 */
	boolean containsBeanDefinition(String beanName);

	/**
	 * Return the number of beans defined in the factory.
	 * <p>Does not consider any hierarchy this factory may participate in,
	 * and ignores any singleton beans that have been registered by
	 * other means than bean definitions.
	 * @return the number of beans defined in the factory
	 */
	int getBeanDefinitionCount();

	/**
	 * Return the names of all beans defined in this factory.
	 * <p>Does not consider any hierarchy this factory may participate in,
	 * and ignores any singleton beans that have been registered by
	 * other means than bean definitions.
	 * @return the names of all beans defined in this factory,
	 * or an empty array if none defined
	 */
	String[] getBeanDefinitionNames();

	/**
	 * Return the names of beans matching the given type (including subclasses),
	 * judging from either bean definitions or the value of {@code getObjectType}
	 * in the case of FactoryBeans.
	 * <p><b>NOTE: This method introspects top-level beans only.</b> It does <i>not</i>
	 * check nested beans which might match the specified type as well.
	 * <p>Does consider objects created by FactoryBeans, which means that FactoryBeans
	 * will get initialized. If the object created by the FactoryBean doesn't match,
	 * the raw FactoryBean itself will be matched against the type.
	 * <p>Does not consider any hierarchy this factory may participate in.
	 * Use BeanFactoryUtils' {@code beanNamesForTypeIncludingAncestors}
	 * to include beans in ancestor factories too.
	 * <p>Note: Does <i>not</i> ignore singleton beans that have been registered
	 * by other means than bean definitions.
	 * <p>This version of {@code getBeanNamesForType} matches all kinds of beans,
	 * be it singletons, prototypes, or FactoryBeans. In most implementations, the
	 * result will be the same as for {@code getBeanNamesForType(type, true, true)}.
	 * <p>Bean names returned by this method should always return bean names <i>in the
	 * order of definition</i> in the backend configuration, as far as possible.
	 * @param type the generically typed class or interface to match
	 * @return the names of beans (or objects created by FactoryBeans) matching
	 * the given object type (including subclasses), or an empty array if none
	 * @since 4.2
	 * @see #isTypeMatch(String, ResolvableType)
	 * @see FactoryBean#getObjectType
	 * @see BeanFactoryUtils#beanNamesForTypeIncludingAncestors(ListableBeanFactory, ResolvableType)
	 */
	String[] getBeanNamesForType(ResolvableType type);

	/**
	 * Return the names of beans matching the given type (including subclasses),
	 * judging from either bean definitions or the value of {@code getObjectType}
	 * in the case of FactoryBeans.
	 * <p><b>NOTE: This method introspects top-level beans only.</b> It does <i>not</i>
	 * check nested beans which might match the specified type as well.
	 * <p>Does consider objects created by FactoryBeans, which means that FactoryBeans
	 * will get initialized. If the object created by the FactoryBean doesn't match,
	 * the raw FactoryBean itself will be matched against the type.
	 * <p>Does not consider any hierarchy this factory may participate in.
	 * Use BeanFactoryUtils' {@code beanNamesForTypeIncludingAncestors}
	 * to include beans in ancestor factories too.
	 * <p>Note: Does <i>not</i> ignore singleton beans that have been registered
	 * by other means than bean definitions.
	 * <p>This version of {@code getBeanNamesForType} matches all kinds of beans,
	 * be it singletons, prototypes, or FactoryBeans. In most implementations, the
	 * result will be the same as for {@code getBeanNamesForType(type, true, true)}.
	 * <p>Bean names returned by this method should always return bean names <i>in the
	 * order of definition</i> in the backend configuration, as far as possible.
	 * @param type the class or interface to match, or {@code null} for all bean names
	 * @return the names of beans (or objects created by FactoryBeans) matching
	 * the given object type (including subclasses), or an empty array if none
	 * @see FactoryBean#getObjectType
	 * @see BeanFactoryUtils#beanNamesForTypeIncludingAncestors(ListableBeanFactory, Class)
	 */
	String[] getBeanNamesForType(@Nullable Class<?> type);

	/**
	 * Return the names of beans matching the given type (including subclasses),
	 * judging from either bean definitions or the value of {@code getObjectType}
	 * in the case of FactoryBeans.
	 * <p><b>NOTE: This method introspects top-level beans only.</b> It does <i>not</i>
	 * check nested beans which might match the specified type as well.
	 * <p>Does consider objects created by FactoryBeans if the "allowEagerInit" flag is set,
	 * which means that FactoryBeans will get initialized. If the object created by the
	 * FactoryBean doesn't match, the raw FactoryBean itself will be matched against the
	 * type. If "allowEagerInit" is not set, only raw FactoryBeans will be checked
	 * (which doesn't require initialization of each FactoryBean).
	 * <p>Does not consider any hierarchy this factory may participate in.
	 * Use BeanFactoryUtils' {@code beanNamesForTypeIncludingAncestors}
	 * to include beans in ancestor factories too.
	 * <p>Note: Does <i>not</i> ignore singleton beans that have been registered
	 * by other means than bean definitions.
	 * <p>Bean names returned by this method should always return bean names <i>in the
	 * order of definition</i> in the backend configuration, as far as possible.
	 * @param type the class or interface to match, or {@code null} for all bean names
	 * @param includeNonSingletons whether to include prototype or scoped beans too
	 * or just singletons (also applies to FactoryBeans)
	 * @param allowEagerInit whether to initialize <i>lazy-init singletons</i> and
	 * <i>objects created by FactoryBeans</i> (or by factory methods with a
	 * "factory-bean" reference) for the type check. Note that FactoryBeans need to be
	 * eagerly initialized to determine their type: So be aware that passing in "true"
	 * for this flag will initialize FactoryBeans and "factory-bean" references.
	 * @return the names of beans (or objects created by FactoryBeans) matching
	 * the given object type (including subclasses), or an empty array if none
	 * @see FactoryBean#getObjectType
	 * @see BeanFactoryUtils#beanNamesForTypeIncludingAncestors(ListableBeanFactory, Class, boolean, boolean)
	 */
	String[] getBeanNamesForType(@Nullable Class<?> type, boolean includeNonSingletons, boolean allowEagerInit);

	/**
	 * Return the bean instances that match the given object type (including
	 * subclasses), judging from either bean definitions or the value of
	 * {@code getObjectType} in the case of FactoryBeans.
	 * <p><b>NOTE: This method introspects top-level beans only.</b> It does <i>not</i>
	 * check nested beans which might match the specified type as well.
	 * <p>Does consider objects created by FactoryBeans, which means that FactoryBeans
	 * will get initialized. If the object created by the FactoryBean doesn't match,
	 * the raw FactoryBean itself will be matched against the type.
	 * <p>Does not consider any hierarchy this factory may participate in.
	 * Use BeanFactoryUtils' {@code beansOfTypeIncludingAncestors}
	 * to include beans in ancestor factories too.
	 * <p>Note: Does <i>not</i> ignore singleton beans that have been registered
	 * by other means than bean definitions.
	 * <p>This version of getBeansOfType matches all kinds of beans, be it
	 * singletons, prototypes, or FactoryBeans. In most implementations, the
	 * result will be the same as for {@code getBeansOfType(type, true, true)}.
	 * <p>The Map returned by this method should always return bean names and
	 * corresponding bean instances <i>in the order of definition</i> in the
	 * backend configuration, as far as possible.
	 * @param type the class or interface to match, or {@code null} for all concrete beans
	 * @return a Map with the matching beans, containing the bean names as
	 * keys and the corresponding bean instances as values
	 * @throws BeansException if a bean could not be created
	 * @since 1.1.2
	 * @see FactoryBean#getObjectType
	 * @see BeanFactoryUtils#beansOfTypeIncludingAncestors(ListableBeanFactory, Class)
	 */
	<T> Map<String, T> getBeansOfType(@Nullable Class<T> type) throws BeansException;

	/**
	 * Return the bean instances that match the given object type (including
	 * subclasses), judging from either bean definitions or the value of
	 * {@code getObjectType} in the case of FactoryBeans.
	 * <p><b>NOTE: This method introspects top-level beans only.</b> It does <i>not</i>
	 * check nested beans which might match the specified type as well.
	 * <p>Does consider objects created by FactoryBeans if the "allowEagerInit" flag is set,
	 * which means that FactoryBeans will get initialized. If the object created by the
	 * FactoryBean doesn't match, the raw FactoryBean itself will be matched against the
	 * type. If "allowEagerInit" is not set, only raw FactoryBeans will be checked
	 * (which doesn't require initialization of each FactoryBean).
	 * <p>Does not consider any hierarchy this factory may participate in.
	 * Use BeanFactoryUtils' {@code beansOfTypeIncludingAncestors}
	 * to include beans in ancestor factories too.
	 * <p>Note: Does <i>not</i> ignore singleton beans that have been registered
	 * by other means than bean definitions.
	 * <p>The Map returned by this method should always return bean names and
	 * corresponding bean instances <i>in the order of definition</i> in the
	 * backend configuration, as far as possible.
	 * @param type the class or interface to match, or {@code null} for all concrete beans
	 * @param includeNonSingletons whether to include prototype or scoped beans too
	 * or just singletons (also applies to FactoryBeans)
	 * @param allowEagerInit whether to initialize <i>lazy-init singletons</i> and
	 * <i>objects created by FactoryBeans</i> (or by factory methods with a
	 * "factory-bean" reference) for the type check. Note that FactoryBeans need to be
	 * eagerly initialized to determine their type: So be aware that passing in "true"
	 * for this flag will initialize FactoryBeans and "factory-bean" references.
	 * @return a Map with the matching beans, containing the bean names as
	 * keys and the corresponding bean instances as values
	 * @throws BeansException if a bean could not be created
	 * @see FactoryBean#getObjectType
	 * @see BeanFactoryUtils#beansOfTypeIncludingAncestors(ListableBeanFactory, Class, boolean, boolean)
	 */
	<T> Map<String, T> getBeansOfType(@Nullable Class<T> type, boolean includeNonSingletons, boolean allowEagerInit)
			throws BeansException;

	/**
	 * Find all names of beans which are annotated with the supplied {@link Annotation}
	 * type, without creating corresponding bean instances yet.
	 * <p>Note that this method considers objects created by FactoryBeans, which means
	 * that FactoryBeans will get initialized in order to determine their object type.
	 * @param annotationType the type of annotation to look for
	 * (at class, interface or factory method level of the specified bean)
	 * @return the names of all matching beans
	 * @since 4.0
	 * @see #findAnnotationOnBean
	 */
	String[] getBeanNamesForAnnotation(Class<? extends Annotation> annotationType);

	/**
	 * Find all beans which are annotated with the supplied {@link Annotation} type,
	 * returning a Map of bean names with corresponding bean instances.
	 * <p>Note that this method considers objects created by FactoryBeans, which means
	 * that FactoryBeans will get initialized in order to determine their object type.
	 * @param annotationType the type of annotation to look for
	 * (at class, interface or factory method level of the specified bean)
	 * @return a Map with the matching beans, containing the bean names as
	 * keys and the corresponding bean instances as values
	 * @throws BeansException if a bean could not be created
	 * @since 3.0
	 * @see #findAnnotationOnBean
	 */
	Map<String, Object> getBeansWithAnnotation(Class<? extends Annotation> annotationType) throws BeansException;

	/**
	 * Find an {@link Annotation} of {@code annotationType} on the specified bean,
	 * traversing its interfaces and super classes if no annotation can be found on
	 * the given class itself, as well as checking the bean's factory method (if any).
	 * @param beanName the name of the bean to look for annotations on
	 * @param annotationType the type of annotation to look for
	 * (at class, interface or factory method level of the specified bean)
	 * @return the annotation of the given type if found, or {@code null} otherwise
	 * @throws NoSuchBeanDefinitionException if there is no bean with the given name
	 * @since 3.0
	 * @see #getBeanNamesForAnnotation
	 * @see #getBeansWithAnnotation
	 */
	@Nullable
	<A extends Annotation> A findAnnotationOnBean(String beanName, Class<A> annotationType)
			throws NoSuchBeanDefinitionException;

}
