Spring源码之BeanFactory

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

/**
 * The root interface for accessing a Spring bean container.
 * This is the basic client view of a bean container;
 * further interfaces such as {@link ListableBeanFactory} and
 * {@link org.springframework.beans.factory.config.ConfigurableBeanFactory}
 * are available for specific purposes.
 * 用于访问SpringBean容器的根接口
 * 这是bean容器的基本客户机视图
 * 扩展接口例如ListableBeanFactory和ConfigurableBeanFactory
 * 可用于特定目的的
 *
 * <p>This interface is implemented by objects that hold a number of bean definitions,
 * each uniquely identified by a String name. Depending on the bean definition,
 * the factory will return either an independent instance of a contained object
 * (the Prototype design pattern), or a single shared instance (a superior
 * alternative to the Singleton design pattern, in which the instance is a
 * singleton in the scope of the factory). Which type of instance will be returned
 * depends on the bean factory configuration: the API is the same. Since Spring
 * 2.0, further scopes are available depending on the concrete application
 * context (e.g. "request" and "session" scopes in a web environment).
 * 这个接口由包含许多bean定义的对象实现
 * 每个都由一个字符串名称唯一标识
 * 通过这个bean的定义,工厂将返回所包含对象的独立实例(原型设计模式)
 * 或单个共享实例(一个优于单例设计模式的选择,其中实例是工厂范围内的单例)
 * 返回哪种类型的实例取决于bean工厂配置
 * API是相同的
 * 自spring 2.0以来,可以根据具体的应用程序上下文使用更多的范围
 *
 * <p>The point of this approach is that the BeanFactory is a central registry
 * of application components, and centralizes configuration of application
 * components (no more do individual objects need to read properties files,
 * for example). See chapters 4 and 11 of "Expert One-on-One J2EE Design and
 * Development" for a discussion of the benefits of this approach.
 * 正中方法的要点是BeanFactory是应用程序组件的中心注册表 和 集中配置应用程序组件
 * (例如,单个对象不再需要读取属性文件)
 * 有关此方法的好处的讨论,请参阅"专家一对一J2EE设计和开发"的第四章和第11章
 *
 * <p>Note that it is generally better to rely on Dependency Injection
 * ("push" configuration) to configure application objects through setters
 * or constructors, rather than use any form of "pull" configuration like a
 * BeanFactory lookup. Spring's Dependency Injection functionality is
 * implemented using this BeanFactory interface and its subinterfaces.
 * 注意:通常依赖注入("push"配置)通过setter或构造函数配置应用程序更好
 * 而不是像BeanFactory查找那样使用任何形式的"pull"配置
 * Spring的依赖注入功能是使用这个BeanFactory接口及其子接口实现的
 *
 * <p>Normally a BeanFactory will load bean definitions stored in a configuration
 * source (such as an XML document), and use the {@code org.springframework.beans}
 * package to configure the beans. However, an implementation could simply return
 * Java objects it creates as necessary directly in Java code. There are no
 * constraints on how the definitions could be stored: LDAP, RDBMS, XML,
 * properties file, etc. Implementations are encouraged to support references
 * amongst beans (Dependency Injection).
 * 通常,BeanFactory将加载存储在配置源(如XML文档)中的bean定义,并使用@code包来配置bean,
 * 但是,实现可以简单地返回它在Java代码中直接创建的Java对象
 * 对于如何存储定义没有限制:LDAP, RDBMS, XML,属性文件等等,
 * 鼓励实现支持bean之间的引用(依赖注入)
 *
 * <p>In contrast to the methods in {@link ListableBeanFactory}, all of the
 * operations in this interface will also check parent factories if this is a
 * {@link HierarchicalBeanFactory}. If a bean is not found in this factory instance,
 * the immediate parent factory will be asked. Beans in this factory instance
 * are supposed to override beans of the same name in any parent factory.
 * 与{ListableBeanFactory}中的方法相反,此接口中的所有操作也将检查父工厂是否为{HierarchicalBeanFactory}
 * 如果在这个工厂实例中没有找到bean,将询问直接的父工厂
 * 这个工厂实例中的bean,应该覆盖任何父工厂中同名的bean
 *
 * <p>Bean factory implementations should support the standard bean lifecycle interfaces
 * as far as possible. The full set of initialization methods and their standard order is:
 * Bean工厂实现应该尽可能支持标准Bean生命周期接口
 * 完整的初始化方法及其标准顺序是:
 * <ol>
 * <li>BeanNameAware's {@code setBeanName}
 * <li>BeanClassLoaderAware's {@code setBeanClassLoader}
 * <li>BeanFactoryAware's {@code setBeanFactory}
 * <li>EnvironmentAware's {@code setEnvironment}
 * <li>EmbeddedValueResolverAware's {@code setEmbeddedValueResolver}
 * <li>ResourceLoaderAware's {@code setResourceLoader}
 * (only applicable when running in an application context)
 * <li>ApplicationEventPublisherAware's {@code setApplicationEventPublisher}
 * (only applicable when running in an application context)
 * <li>MessageSourceAware's {@code setMessageSource}
 * (only applicable when running in an application context)
 * <li>ApplicationContextAware's {@code setApplicationContext}
 * (only applicable when running in an application context)
 * <li>ServletContextAware's {@code setServletContext}
 * (only applicable when running in a web application context)
 * <li>{@code postProcessBeforeInitialization} methods of BeanPostProcessors
 * <li>InitializingBean's {@code afterPropertiesSet}
 * <li>a custom init-method definition
 * <li>{@code postProcessAfterInitialization} methods of BeanPostProcessors
 * </ol>
 *
 * <p>On shutdown of a bean factory, the following lifecycle methods apply:
 * <ol>
 * <li>{@code postProcessBeforeDestruction} methods of DestructionAwareBeanPostProcessors
 * <li>DisposableBean's {@code destroy}
 * <li>a custom destroy-method definition
 * </ol>
 *
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @author Chris Beams
 * @since 13 April 2001
 * @see BeanNameAware#setBeanName
 * @see BeanClassLoaderAware#setBeanClassLoader
 * @see BeanFactoryAware#setBeanFactory
 * @see org.springframework.context.ResourceLoaderAware#setResourceLoader
 * @see org.springframework.context.ApplicationEventPublisherAware#setApplicationEventPublisher
 * @see org.springframework.context.MessageSourceAware#setMessageSource
 * @see org.springframework.context.ApplicationContextAware#setApplicationContext
 * @see org.springframework.web.context.ServletContextAware#setServletContext
 * @see org.springframework.beans.factory.config.BeanPostProcessor#postProcessBeforeInitialization
 * @see InitializingBean#afterPropertiesSet
 * @see org.springframework.beans.factory.support.RootBeanDefinition#getInitMethodName
 * @see org.springframework.beans.factory.config.BeanPostProcessor#postProcessAfterInitialization
 * @see DisposableBean#destroy
 * @see org.springframework.beans.factory.support.RootBeanDefinition#getDestroyMethodName
 */
public interface BeanFactory {

    /**
     * Used to dereference a {@link FactoryBean} instance and distinguish it from
     * beans <i>created</i> by the FactoryBean. For example, if the bean named
     * {@code myJndiObject} is a FactoryBean, getting {@code &myJndiObject}
     * will return the factory, not the instance returned by the factory.
     * 用于取消对实例的引用,并通过FactoryBean将其与bean区分开来
     * 例如:如果这个bean的名字是myJndiObject它是一个FactoryBean,通过getting(&myJndiObject)
     * 将会返回这个工厂,而不是返回这个工厂的实例;
     *
     */
    String FACTORY_BEAN_PREFIX = "&";


    /**
     * Return an instance, which may be shared or independent, of the specified bean.
     * <p>This method allows a Spring BeanFactory to be used as a replacement for the
     * Singleton or Prototype design pattern. Callers may retain references to
     * returned objects in the case of Singleton beans.
     * <p>Translates aliases back to the corresponding canonical bean name.
     * Will ask the parent factory if the bean cannot be found in this factory instance.
     * @param name the name of the bean to retrieve
     * @return an instance of the bean
     * @throws NoSuchBeanDefinitionException if there is no bean with the specified name
     * @throws BeansException if the bean could not be obtained
     * 返回指定bean的一个实例,该实例可以是共享的,也可以是独立的;
     * 该方法允许使用Spring BeanFactory作为单例或原型设计模式的替代,
     * 在单例bean的情况下,调用者可以保留对返回对象的引用.
     * 将别名翻译回相应的规范bean名称,
     * 将询问父工厂是否在此工厂实例中找不到bean.
     *
     */
    Object getBean(String name) throws BeansException;

    /**
     * Return an instance, which may be shared or independent, of the specified bean.
     * <p>Behaves the same as {@link #getBean(String)}, but provides a measure of type
     * safety by throwing a BeanNotOfRequiredTypeException if the bean is not of the
     * required type. This means that ClassCastException can't be thrown on casting
     * the result correctly, as can happen with {@link #getBean(String)}.
     * <p>Translates aliases back to the corresponding canonical bean name.
     * Will ask the parent factory if the bean cannot be found in this factory instance.
     * @param name the name of the bean to retrieve
     * @param requiredType type the bean must match; can be an interface or superclass
     * @return an instance of the bean
     * @throws NoSuchBeanDefinitionException if there is no such bean definition
     * @throws BeanNotOfRequiredTypeException if the bean is not of the required type
     * @throws BeansException if the bean could not be created
     * 返回指定bean的一个实例,该实例可以是共享的也可以是独立的;
     * 行为与getBean()相同,但是如果bean不是必需的类型,则通过抛出BeanNotOfRequiredTypeException
     * 来提供类型安全性的度量
     * 这意味着ClassCastException不能像getBean()那样在正确的转换结果时抛出
     * 将别名翻译回相应的规范bean名称
     * 将询问父工厂是否在此工厂实例中找不到bean;
     */
    <T> T getBean(String name, Class<T> requiredType) throws BeansException;

    /**
     * Return an instance, which may be shared or independent, of the specified bean.
     * <p>Allows for specifying explicit constructor arguments / factory method arguments,
     * overriding the specified default arguments (if any) in the bean definition.
     * @param name the name of the bean to retrieve
     * @param args arguments to use when creating a bean instance using explicit arguments
     * (only applied when creating a new instance as opposed to retrieving an existing one)
     * @return an instance of the bean
     * @throws NoSuchBeanDefinitionException if there is no such bean definition
     * @throws BeanDefinitionStoreException if arguments have been given but
     * the affected bean isn't a prototype
     * @throws BeansException if the bean could not be created
     * @since 2.5
     * 返回指定bean的一个实例,该实例可以是共享的也可以是独立的;
     * 允许指定显式构造函数参数/工厂方法参数,
     * 覆盖bean定义中指定的默认参数(如果有的话)
     */
    Object getBean(String name, Object... args) throws BeansException;

    /**
     * Return the bean instance that uniquely matches the given object type, if any.
     * <p>This method goes into {@link ListableBeanFactory} by-type lookup territory
     * but may also be translated into a conventional by-name lookup based on the name
     * of the given type. For more extensive retrieval operations across sets of beans,
     * use {@link ListableBeanFactory} and/or {@link BeanFactoryUtils}.
     * @param requiredType type the bean must match; can be an interface or superclass
     * @return an instance of the single bean matching the required type
     * @throws NoSuchBeanDefinitionException if no bean of the given type was found
     * @throws NoUniqueBeanDefinitionException if more than one bean of the given type was found
     * @throws BeansException if the bean could not be created
     * @since 3.0
     * @see ListableBeanFactory
     * 返回唯一匹配给定对象类型的bean实例,如果有的话
     * 该方法进入ListableBeanFactory的按类型查找领域,
     * 但是也可以根据给定类型的名称转换为传统的按名称查找
     * 用于跨bean集进行更广泛的检索操作
     * 通过使用ListableBeanFactory或者BeanFactoryUtils
     */
    <T> T getBean(Class<T> requiredType) throws BeansException;

    /**
     * Return an instance, which may be shared or independent, of the specified bean.
     * <p>Allows for specifying explicit constructor arguments / factory method arguments,
     * overriding the specified default arguments (if any) in the bean definition.
     * <p>This method goes into {@link ListableBeanFactory} by-type lookup territory
     * but may also be translated into a conventional by-name lookup based on the name
     * of the given type. For more extensive retrieval operations across sets of beans,
     * use {@link ListableBeanFactory} and/or {@link BeanFactoryUtils}.
     * @param requiredType type the bean must match; can be an interface or superclass
     * @param args arguments to use when creating a bean instance using explicit arguments
     * (only applied when creating a new instance as opposed to retrieving an existing one)
     * @return an instance of the bean
     * @throws NoSuchBeanDefinitionException if there is no such bean definition
     * @throws BeanDefinitionStoreException if arguments have been given but
     * the affected bean isn't a prototype
     * @throws BeansException if the bean could not be created
     * @since 4.1
     * 返回指定bean的一个实例,该实例可以是共享的也可以是独立的;
     * 允许指定显式构造函数参数/工厂方法参数,
     * 覆盖bean定义中指定的默认参数(如果有的话)
     * 该方法进入ListableBeanFactory的按类型查找领域,
     * 但是也可以根据给定类型的名称转换为传统的按名称查找
     * 用于跨bean集进行更广泛的检索操作
     * 通过使用ListableBeanFactory或者BeanFactoryUtils
     */
    <T> T getBean(Class<T> requiredType, Object... args) throws BeansException;

    /**
     * Return a provider for the specified bean, allowing for lazy on-demand retrieval
     * of instances, including availability and uniqueness options.
     * @param requiredType type the bean must match; can be an interface or superclass
     * @return a corresponding provider handle
     * @since 5.1
     * @see #getBeanProvider(ResolvableType)
     * 返回指定bean的提供程序,允许延迟按需检索实例,包括可用性和唯一性选项
     */
    <T> ObjectProvider<T> getBeanProvider(Class<T> requiredType);

    /**
     * Return a provider for the specified bean, allowing for lazy on-demand retrieval
     * of instances, including availability and uniqueness options.
     * @param requiredType type the bean must match; can be a generic type declaration.
     * Note that collection types are not supported here, in contrast to reflective
     * injection points. For programmatically retrieving a list of beans matching a
     * specific type, specify the actual bean type as an argument here and subsequently
     * use {@link ObjectProvider#orderedStream()} or its lazy streaming/iteration options.
     * @return a corresponding provider handle
     * @since 5.1
     * @see ObjectProvider#iterator()
     * @see ObjectProvider#stream()
     * @see ObjectProvider#orderedStream()
     * 返回指定bean的提供程序,允许延迟按需检索实例,包括可用性和唯一性选项
     */
    <T> ObjectProvider<T> getBeanProvider(ResolvableType requiredType);

    /**
     * Does this bean factory contain a bean definition or externally registered singleton
     * instance with the given name?
     * <p>If the given name is an alias, it will be translated back to the corresponding
     * canonical bean name.
     * <p>If this factory is hierarchical, will ask any parent factory if the bean cannot
     * be found in this factory instance.
     * <p>If a bean definition or singleton instance matching the given name is found,
     * this method will return {@code true} whether the named bean definition is concrete
     * or abstract, lazy or eager, in scope or not. Therefore, note that a {@code true}
     * return value from this method does not necessarily indicate that {@link #getBean}
     * will be able to obtain an instance for the same name.
     * @param name the name of the bean to query
     * @return whether a bean with the given name is present
     * 这个bean工厂是否包含一个bean定义或外部注册的具有给定名称的单例实例?
     * 如果给定的名称是别名,它将被转换为相应的规范bean名称
     * 如果这个工厂是分层的,将询问任何父工厂是否在这个工厂实例中找不到bean
     * 如果找到与给定名称匹配的bean定义或单例实例,该方法将返回true,无论指定的bean定义是具体的还是抽象的,
     * 是延迟的还是热切的,在作用域上是否如此,
     * 然而,请注意,这个方法的true返回值并不一定标识{getBean}能够获得同名的实例
     */
    boolean containsBean(String name);

    /**
     * Is this bean a shared singleton? That is, will {@link #getBean} always
     * return the same instance?
     * <p>Note: This method returning {@code false} does not clearly indicate
     * independent instances. It indicates non-singleton instances, which may correspond
     * to a scoped bean as well. Use the {@link #isPrototype} operation to explicitly
     * check for independent instances.
     * <p>Translates aliases back to the corresponding canonical bean name.
     * Will ask the parent factory if the bean cannot be found in this factory instance.
     * @param name the name of the bean to query
     * @return whether this bean corresponds to a singleton instance
     * @throws NoSuchBeanDefinitionException if there is no bean with the given name
     * @see #getBean
     * @see #isPrototype
     * 这是一个共享的单例bean吗?也就是说{getBean}总是返回相同的实例吗?
     * 注意:这个返回{false}的方法并不清楚的表示独立的实例,
     * 它指出了非单例实例,这也可能对应于一个作用域bean
     * 使用{isPrototype}操作显式地检查独立实例
     * 将别名翻译成相应的规范bean名称
     * 将询问父工厂是否在此工厂实例中找不到bean.
     */
    boolean isSingleton(String name) throws NoSuchBeanDefinitionException;

    /**
     * Is this bean a prototype? That is, will {@link #getBean} always return
     * independent instances?
     * <p>Note: This method returning {@code false} does not clearly indicate
     * a singleton object. It indicates non-independent instances, which may correspond
     * to a scoped bean as well. Use the {@link #isSingleton} operation to explicitly
     * check for a shared singleton instance.
     * <p>Translates aliases back to the corresponding canonical bean name.
     * Will ask the parent factory if the bean cannot be found in this factory instance.
     * @param name the name of the bean to query
     * @return whether this bean will always deliver independent instances
     * @throws NoSuchBeanDefinitionException if there is no bean with the given name
     * @since 2.0.3
     * @see #getBean
     * @see #isSingleton
     * 这个bean是原型吗?也就是说,{getBean}总是返回独立的实例
     * 注意:这个返回{false}的方法并不清楚的表示一个单例对象
     * 它指示非独立的实例,这些实例也可能对应于作用域的bean
     * 使用{isSingleton}操作显示的检查共享的单例实例
     * 将别名翻译成相应的规范bean名称
     * 将询问父工厂是否在此工厂实例中找不到bean
     */
    boolean isPrototype(String name) throws NoSuchBeanDefinitionException;

    /**
     * Check whether the bean with the given name matches the specified type.
     * More specifically, check whether a {@link #getBean} call for the given name
     * would return an object that is assignable to the specified target type.
     * <p>Translates aliases back to the corresponding canonical bean name.
     * Will ask the parent factory if the bean cannot be found in this factory instance.
     * @param name the name of the bean to query
     * @param typeToMatch the type to match against (as a {@code ResolvableType})
     * @return {@code true} if the bean type matches,
     * {@code false} if it doesn't match or cannot be determined yet
     * @throws NoSuchBeanDefinitionException if there is no bean with the given name
     * @since 4.2
     * @see #getBean
     * @see #getType
     * 检查具有给定名称的bean是否匹配指定的类型
     * 更具体地说,检查对于给定名称的{getBean}调用是否会返回可分配给指定目标类型的对象;
     * 将别名翻译成相应的规范bean名称
     * 将询问父工厂是否在此工厂实例中找不到bean
     */
    boolean isTypeMatch(String name, ResolvableType typeToMatch) throws NoSuchBeanDefinitionException;

    /**
     * Check whether the bean with the given name matches the specified type.
     * More specifically, check whether a {@link #getBean} call for the given name
     * would return an object that is assignable to the specified target type.
     * <p>Translates aliases back to the corresponding canonical bean name.
     * Will ask the parent factory if the bean cannot be found in this factory instance.
     * @param name the name of the bean to query
     * @param typeToMatch the type to match against (as a {@code Class})
     * @return {@code true} if the bean type matches,
     * {@code false} if it doesn't match or cannot be determined yet
     * @throws NoSuchBeanDefinitionException if there is no bean with the given name
     * @since 2.0.1
     * @see #getBean
     * @see #getType
     */
    boolean isTypeMatch(String name, Class<?> typeToMatch) throws NoSuchBeanDefinitionException;

    /**
     * Determine the type of the bean with the given name. More specifically,
     * determine the type of object that {@link #getBean} would return for the given name.
     * <p>For a {@link FactoryBean}, return the type of object that the FactoryBean creates,
     * as exposed by {@link FactoryBean#getObjectType()}. This may lead to the initialization
     * of a previously uninitialized {@code FactoryBean} (see {@link #getType(String, boolean)}).
     * <p>Translates aliases back to the corresponding canonical bean name.
     * Will ask the parent factory if the bean cannot be found in this factory instance.
     * @param name the name of the bean to query
     * @return the type of the bean, or {@code null} if not determinable
     * @throws NoSuchBeanDefinitionException if there is no bean with the given name
     * @since 1.1.2
     * @see #getBean
     * @see #isTypeMatch
     * 确定具有给定名称的bean的类型,更具体地说,确定{getBean}为给定名称返回的对象类型.
     * 对于{FactoryBean},返回FactoryBean创建的对象类型,由{FactoryBean的getObjectType()}公开;
     * 这可能导致前面未初始化的{FactoryBean}的初始化(参见{getType(String,boolean)}).
     * 将别名翻译成相应的规范bean名称
     * 将询问父工厂是否在此工厂实例中找不到bean
     */
    @Nullable
    Class<?> getType(String name) throws NoSuchBeanDefinitionException;

    /**
     * Determine the type of the bean with the given name. More specifically,
     * determine the type of object that {@link #getBean} would return for the given name.
     * <p>For a {@link FactoryBean}, return the type of object that the FactoryBean creates,
     * as exposed by {@link FactoryBean#getObjectType()}. Depending on the
     * {@code allowFactoryBeanInit} flag, this may lead to the initialization of a previously
     * uninitialized {@code FactoryBean} if no early type information is available.
     * <p>Translates aliases back to the corresponding canonical bean name.
     * Will ask the parent factory if the bean cannot be found in this factory instance.
     * @param name the name of the bean to query
     * @param allowFactoryBeanInit whether a {@code FactoryBean} may get initialized
     * just for the purpose of determining its object type
     * @return the type of the bean, or {@code null} if not determinable
     * @throws NoSuchBeanDefinitionException if there is no bean with the given name
     * @since 5.2
     * @see #getBean
     * @see #isTypeMatch
     * 确定具有给定名称的bean类型.更具体地说,确定{getBean}为给定名称返回的对象类型.
     * 对于{FactoryBean},返回FactoryBean创建的对象的类型,由{FactoryBean的getObjectType()}公开.
     * 根据{allowFactoryBeanInit}标志,如果没有可用的早期类型信息,这可能会导致初始化以前,未初始化的{FactoryBean}
     * 将别名翻译成相应的规范bean名称,
     * 将询问父工厂是否在此工厂实例中找不到bean.
     */
    @Nullable
    Class<?> getType(String name, boolean allowFactoryBeanInit) throws NoSuchBeanDefinitionException;

    /**
     * Return the aliases for the given bean name, if any.
     * All of those aliases point to the same bean when used in a {@link #getBean} call.
     * <p>If the given name is an alias, the corresponding original bean name
     * and other aliases (if any) will be returned, with the original bean name
     * being the first element in the array.
     * <p>Will ask the parent factory if the bean cannot be found in this factory instance.
     * @param name the bean name to check for aliases
     * @return the aliases, or an empty array if none
     * @see #getBean
     * 返回给定bean名称的别名,如果有的话.
     * 当在{getBean}调用中使用时,所有这些别名都指向同一个bean;
     * 如果给定的名称是别名,则返回相应的原始bean名称和其他别名(如果与),原始bean名称是数字中的第一个元素.
     * 将询问父工厂是否在此工厂实例中找不到bean;
     */
    String[] getAliases(String name);

}