org.springframework.beans.factory.config

## 接口 SingletonBeanRegistry

- 所有已知子接口:
    ConfigurableBeanFactory, ConfigurableListableBeanFactory
  所有已知实现类:
    AbstractAutowireCapableBeanFactory, AbstractBeanFactory, DefaultListableBeanFactory, DefaultSingletonBeanRegistry, FactoryBeanRegistrySupport, XmlBeanFactory

      public interface SingletonBeanRegistry

  Interface that defines a registry for shared bean instances. Can be implemented by `BeanFactory` implementations in order to expose their singleton management facility in a uniform manner.

  The `ConfigurableBeanFactory` interface extends this interface.

  从以下版本开始:
    2.0
  作者:
    Juergen Hoeller
  另请参阅:
    `ConfigurableBeanFactory`, `DefaultSingletonBeanRegistry`, `AbstractBeanFactory`

- - ### 方法概要

    所有方法 实例方法 抽象方法
    限定符和类型 | 方法和说明
    --- | ---
    `boolean` | `containsSingleton(String beanName)` Check if this registry contains a singleton instance with the given name.
    `Object` | `getSingleton(String beanName)` Return the (raw) singleton object registered under the given name.
    `int` | `getSingletonCount()` Return the number of singleton beans registered in this registry.
    `Object` | `getSingletonMutex()` Return the singleton mutex used by this registry (for external collaborators).
    `String[]` | `getSingletonNames()` Return the names of singleton beans registered in this registry.
    `void` | `registerSingleton(String beanName, Object singletonObject)` Register the given existing object as singleton in the bean registry, under the given bean name.

- - ### 方法详细资料

    - #### registerSingleton

          void registerSingleton(String beanName,
                                 Object singletonObject)

      Register the given existing object as singleton in the bean registry, under the given bean name.

      The given instance is supposed to be fully initialized; the registry will not perform any initialization callbacks (in particular, it won't call InitializingBean's `afterPropertiesSet` method). The given instance will not receive any destruction callbacks (like DisposableBean's `destroy` method) either.

      When running within a full BeanFactory: Register a bean definition instead of an existing instance if your bean is supposed to receive initialization and/or destruction callbacks.

      Typically invoked during registry configuration, but can also be used for runtime registration of singletons. As a consequence, a registry implementation should synchronize singleton access; it will have to do this anyway if it supports a BeanFactory's lazy initialization of singletons.

      参数:
        `beanName` - the name of the bean
        `singletonObject` - the existing singleton object
      另请参阅:
        `InitializingBean.afterPropertiesSet()`, `DisposableBean.destroy()`, `BeanDefinitionRegistry.registerBeanDefinition(java.lang.String, org.springframework.beans.factory.config.BeanDefinition)`

    - #### getSingleton

          @Nullable
          Object getSingleton(String beanName)

      Return the (raw) singleton object registered under the given name.

      Only checks already instantiated singletons; does not return an Object for singleton bean definitions which have not been instantiated yet.

      The main purpose of this method is to access manually registered singletons (see `registerSingleton(java.lang.String, java.lang.Object)`). Can also be used to access a singleton defined by a bean definition that already been created, in a raw fashion.

      NOTE: This lookup method is not aware of FactoryBean prefixes or aliases. You need to resolve the canonical bean name first before obtaining the singleton instance.

      参数:
        `beanName` - the name of the bean to look for
      返回:
        the registered singleton object, or `null` if none found
      另请参阅:
        `ConfigurableListableBeanFactory.getBeanDefinition(java.lang.String)`

    - #### containsSingleton

          boolean containsSingleton(String beanName)

      Check if this registry contains a singleton instance with the given name.

      Only checks already instantiated singletons; does not return `true` for singleton bean definitions which have not been instantiated yet.

      The main purpose of this method is to check manually registered singletons (see `registerSingleton(java.lang.String, java.lang.Object)`). Can also be used to check whether a singleton defined by a bean definition has already been created.

      To check whether a bean factory contains a bean definition with a given name, use ListableBeanFactory's `containsBeanDefinition`. Calling both `containsBeanDefinition` and `containsSingleton` answers whether a specific bean factory contains a local bean instance with the given name.

      Use BeanFactory's `containsBean` for general checks whether the factory knows about a bean with a given name (whether manually registered singleton instance or created by bean definition), also checking ancestor factories.

      NOTE: This lookup method is not aware of FactoryBean prefixes or aliases. You need to resolve the canonical bean name first before checking the singleton status.

      参数:
        `beanName` - the name of the bean to look for
      返回:
        if this bean factory contains a singleton instance with the given name
      另请参阅:
        `registerSingleton(java.lang.String, java.lang.Object)`, `ListableBeanFactory.containsBeanDefinition(java.lang.String)`, `BeanFactory.containsBean(java.lang.String)`

    - #### getSingletonNames

          String[] getSingletonNames()

      Return the names of singleton beans registered in this registry.

      Only checks already instantiated singletons; does not return names for singleton bean definitions which have not been instantiated yet.

      The main purpose of this method is to check manually registered singletons (see `registerSingleton(java.lang.String, java.lang.Object)`). Can also be used to check which singletons defined by a bean definition have already been created.

      返回:
        the list of names as a String array (never `null`)
      另请参阅:
        `registerSingleton(java.lang.String, java.lang.Object)`, `BeanDefinitionRegistry.getBeanDefinitionNames()`, `ListableBeanFactory.getBeanDefinitionNames()`

    - #### getSingletonCount

          int getSingletonCount()

      Return the number of singleton beans registered in this registry.

      Only checks already instantiated singletons; does not count singleton bean definitions which have not been instantiated yet.

      The main purpose of this method is to check manually registered singletons (see `registerSingleton(java.lang.String, java.lang.Object)`). Can also be used to count the number of singletons defined by a bean definition that have already been created.

      返回:
        the number of singleton beans
      另请参阅:
        `registerSingleton(java.lang.String, java.lang.Object)`, `BeanDefinitionRegistry.getBeanDefinitionCount()`, `ListableBeanFactory.getBeanDefinitionCount()`

    - #### getSingletonMutex

          Object getSingletonMutex()

      Return the singleton mutex used by this registry (for external collaborators).
      返回:
        the mutex object (never `null`)
      从以下版本开始:
        4.2