org.springframework.beans.factory.config

## 类 FieldRetrievingFactoryBean

- java.lang.Object
- - org.springframework.beans.factory.config.FieldRetrievingFactoryBean

- 所有已实现的接口:
    Aware, BeanClassLoaderAware, BeanNameAware, FactoryBean<Object>, InitializingBean

      public class FieldRetrievingFactoryBean
      extends Object
      implements FactoryBean<Object>, BeanNameAware, BeanClassLoaderAware, InitializingBean

  `FactoryBean` which retrieves a static or non-static field value.

  Typically used for retrieving public static final constants. Usage example:

      // standard definition for exposing a static field, specifying the "staticField" property
       <bean id="myField" class="org.springframework.beans.factory.config.FieldRetrievingFactoryBean">
         <property name="staticField" value="java.sql.Connection.TRANSACTION_SERIALIZABLE"/>
       </bean>

       // convenience version that specifies a static field pattern as bean name
       <bean id="java.sql.Connection.TRANSACTION_SERIALIZABLE"
             class="org.springframework.beans.factory.config.FieldRetrievingFactoryBean"/>

  If you are using Spring 2.0, you can also use the following style of configuration for public static fields.

      <util:constant static-field="java.sql.Connection.TRANSACTION_SERIALIZABLE"/>

  从以下版本开始:
    1.1
  作者:
    Juergen Hoeller
  另请参阅:
    `setStaticField(java.lang.String)`

- - ### 构造器概要

    构造器
    构造器和说明
    `FieldRetrievingFactoryBean()`

  - ### 方法概要

    所有方法 实例方法 具体方法
    限定符和类型 | 方法和说明
    --- | ---
    `void` | `afterPropertiesSet()` Invoked by the containing `BeanFactory` after it has set all bean properties and satisfied `BeanFactoryAware`, `ApplicationContextAware` etc.
    `Object` | `getObject()` Return an instance (possibly shared or independent) of the object managed by this factory.
    `Class<?>` | `getObjectType()` Return the type of object that this FactoryBean creates, or `null` if not known in advance.
    `Class<?>` | `getTargetClass()` Return the target class on which the field is defined.
    `String` | `getTargetField()` Return the name of the field to be retrieved.
    `Object` | `getTargetObject()` Return the target object on which the field is defined.
    `boolean` | `isSingleton()` Is the object managed by this factory a singleton?
    `void` | `setBeanClassLoader(ClassLoader classLoader)` Callback that supplies the bean `class loader` to a bean instance.
    `void` | `setBeanName(String beanName)` The bean name of this FieldRetrievingFactoryBean will be interpreted as "staticField" pattern, if neither "targetClass" nor "targetObject" nor "targetField" have been specified.
    `void` | `setStaticField(String staticField)` Set a fully qualified static field name to retrieve, e.g.
    `void` | `setTargetClass(Class<?> targetClass)` Set the target class on which the field is defined.
    `void` | `setTargetField(String targetField)` Set the name of the field to be retrieved.
    `void` | `setTargetObject(Object targetObject)` Set the target object on which the field is defined.

    - ### 从类继承的方法 java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### 构造器详细资料

    - #### FieldRetrievingFactoryBean

          public FieldRetrievingFactoryBean()

  - ### 方法详细资料

    - #### setTargetClass

          public void setTargetClass(@Nullable
                                     Class<?> targetClass)

      Set the target class on which the field is defined. Only necessary when the target field is static; else, a target object needs to be specified anyway.
      另请参阅:
        `setTargetObject(java.lang.Object)`, `setTargetField(java.lang.String)`

    - #### getTargetClass

          @Nullable
          public Class<?> getTargetClass()

      Return the target class on which the field is defined.

    - #### setTargetObject

          public void setTargetObject(@Nullable
                                      Object targetObject)

      Set the target object on which the field is defined. Only necessary when the target field is not static; else, a target class is sufficient.
      另请参阅:
        `setTargetClass(java.lang.Class<?>)`, `setTargetField(java.lang.String)`

    - #### getTargetObject

          @Nullable
          public Object getTargetObject()

      Return the target object on which the field is defined.

    - #### setTargetField

          public void setTargetField(@Nullable
                                     String targetField)

      Set the name of the field to be retrieved. Refers to either a static field or a non-static field, depending on a target object being set.
      另请参阅:
        `setTargetClass(java.lang.Class<?>)`, `setTargetObject(java.lang.Object)`

    - #### getTargetField

          @Nullable
          public String getTargetField()

      Return the name of the field to be retrieved.

    - #### setStaticField

          public void setStaticField(String staticField)

      Set a fully qualified static field name to retrieve, e.g. "example.MyExampleClass.MY_EXAMPLE_FIELD". Convenient alternative to specifying targetClass and targetField.
      另请参阅:
        `setTargetClass(java.lang.Class<?>)`, `setTargetField(java.lang.String)`

    - #### setBeanName

          public void setBeanName(String beanName)

      The bean name of this FieldRetrievingFactoryBean will be interpreted as "staticField" pattern, if neither "targetClass" nor "targetObject" nor "targetField" have been specified. This allows for concise bean definitions with just an id/name.
      指定者:
        `setBeanName` 在接口中 `BeanNameAware`
      参数:
        `beanName` - the name of the bean in the factory. Note that this name is the actual bean name used in the factory, which may differ from the originally specified name: in particular for inner bean names, the actual bean name might have been made unique through appending "#..." suffixes. Use the `BeanFactoryUtils.originalBeanName(String)` method to extract the original bean name (without suffix), if desired.

    - #### setBeanClassLoader

          public void setBeanClassLoader(ClassLoader classLoader)

      从接口复制的说明: `BeanClassLoaderAware`
      Callback that supplies the bean `class loader` to a bean instance.

      Invoked after the population of normal bean properties but before an initialization callback such as `InitializingBean's` `InitializingBean.afterPropertiesSet()` method or a custom init-method.

      指定者:
        `setBeanClassLoader` 在接口中 `BeanClassLoaderAware`
      参数:
        `classLoader` - the owning class loader

    - #### afterPropertiesSet

          public void afterPropertiesSet()
                                  throws ClassNotFoundException,
                                         NoSuchFieldException

      从接口复制的说明: `InitializingBean`
      Invoked by the containing `BeanFactory` after it has set all bean properties and satisfied `BeanFactoryAware`, `ApplicationContextAware` etc.

      This method allows the bean instance to perform validation of its overall configuration and final initialization when all bean properties have been set.

      指定者:
        `afterPropertiesSet` 在接口中 `InitializingBean`
      抛出:
        `ClassNotFoundException`
        `NoSuchFieldException`

    - #### getObject

          @Nullable
          public Object getObject()
                                      throws IllegalAccessException

      从接口复制的说明: `FactoryBean`
      Return an instance (possibly shared or independent) of the object managed by this factory.

      As with a `BeanFactory`, this allows support for both the Singleton and Prototype design pattern.

      If this FactoryBean is not fully initialized yet at the time of the call (for example because it is involved in a circular reference), throw a corresponding `FactoryBeanNotInitializedException`.

      As of Spring 2.0, FactoryBeans are allowed to return `null` objects. The factory will consider this as normal value to be used; it will not throw a FactoryBeanNotInitializedException in this case anymore. FactoryBean implementations are encouraged to throw FactoryBeanNotInitializedException themselves now, as appropriate.

      指定者:
        `getObject` 在接口中 `FactoryBean<Object>`
      返回:
        an instance of the bean (can be `null`)
      抛出:
        `IllegalAccessException`
      另请参阅:
        `FactoryBeanNotInitializedException`

    - #### getObjectType

          public Class<?> getObjectType()

      从接口复制的说明: `FactoryBean`
      Return the type of object that this FactoryBean creates, or `null` if not known in advance.

      This allows one to check for specific types of beans without instantiating objects, for example on autowiring.

      In the case of implementations that are creating a singleton object, this method should try to avoid singleton creation as far as possible; it should rather estimate the type in advance. For prototypes, returning a meaningful type here is advisable too.

      This method can be called before this FactoryBean has been fully initialized. It must not rely on state created during initialization; of course, it can still use such state if available.

      NOTE: Autowiring will simply ignore FactoryBeans that return `null` here. Therefore it is highly recommended to implement this method properly, using the current state of the FactoryBean.

      指定者:
        `getObjectType` 在接口中 `FactoryBean<Object>`
      返回:
        the type of object that this FactoryBean creates, or `null` if not known at the time of the call
      另请参阅:
        `ListableBeanFactory.getBeansOfType(java.lang.Class<T>)`

    - #### isSingleton

          public boolean isSingleton()

      从接口复制的说明: `FactoryBean`
      Is the object managed by this factory a singleton? That is, will `FactoryBean.getObject()` always return the same object (a reference that can be cached)?

      NOTE: If a FactoryBean indicates to hold a singleton object, the object returned from `getObject()` might get cached by the owning BeanFactory. Hence, do not return `true` unless the FactoryBean always exposes the same reference.

      The singleton status of the FactoryBean itself will generally be provided by the owning BeanFactory; usually, it has to be defined as singleton there.

      NOTE: This method returning `false` does not necessarily indicate that returned objects are independent instances. An implementation of the extended `SmartFactoryBean` interface may explicitly indicate independent instances through its `SmartFactoryBean.isPrototype()` method. Plain `FactoryBean` implementations which do not implement this extended interface are simply assumed to always return independent instances if the `isSingleton()` implementation returns `false`.

      The default implementation returns `true`, since a `FactoryBean` typically manages a singleton instance.

      指定者:
        `isSingleton` 在接口中 `FactoryBean<Object>`
      返回:
        whether the exposed object is a singleton
      另请参阅:
        `FactoryBean.getObject()`, `SmartFactoryBean.isPrototype()`