org.springframework.beans.factory.config

## 类 ServiceLocatorFactoryBean

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

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

      public class ServiceLocatorFactoryBean
      extends Object
      implements FactoryBean<Object>, BeanFactoryAware, InitializingBean

  A `FactoryBean` implementation that takes an interface which must have one or more methods with the signatures `MyType xxx()` or `MyType xxx(MyIdType id)` (typically, `MyService getService()` or `MyService getService(String id)`) and creates a dynamic proxy which implements that interface, delegating to an underlying `BeanFactory`.

  Such service locators permit the decoupling of calling code from the `BeanFactory` API, by using an appropriate custom locator interface. They will typically be used for prototype beans, i.e. for factory methods that are supposed to return a new instance for each call. The client receives a reference to the service locator via setter or constructor injection, to be able to invoke the locator's factory methods on demand. For singleton beans, direct setter or constructor injection of the target bean is preferable.

  On invocation of the no-arg factory method, or the single-arg factory method with a String id of `null` or empty String, if exactly one bean in the factory matches the return type of the factory method, that bean is returned, otherwise a `NoSuchBeanDefinitionException` is thrown.

  On invocation of the single-arg factory method with a non-null (and non-empty) argument, the proxy returns the result of a `BeanFactory.getBean(String)` call, using a stringified version of the passed-in id as bean name.

  A factory method argument will usually be a String, but can also be an int or a custom enumeration type, for example, stringified via `toString`. The resulting String can be used as bean name as-is, provided that corresponding beans are defined in the bean factory. Alternatively, a custom mapping between service IDs and bean names can be defined.

  By way of an example, consider the following service locator interface. Note that this interface is not dependent on any Spring APIs.

      package a.b.c;

      public interface ServiceFactory {

          public MyService getService();
      }

  A sample config in an XML-based `BeanFactory` might look as follows:

      <beans>

         <!-- Prototype bean since we have state -->
         <bean id="myService" class="a.b.c.MyService" singleton="false"/>

         <!-- will lookup the above 'myService' bean by *TYPE* -->
         <bean id="myServiceFactory"
                  class="org.springframework.beans.factory.config.ServiceLocatorFactoryBean">
           <property name="serviceLocatorInterface" value="a.b.c.ServiceFactory"/>
         </bean>

         <bean id="clientBean" class="a.b.c.MyClientBean">
           <property name="myServiceFactory" ref="myServiceFactory"/>
         </bean>

      </beans>

  The attendant `MyClientBean` class implementation might then look something like this:

      package a.b.c;

      public class MyClientBean {

          private ServiceFactory myServiceFactory;

          // actual implementation provided by the Spring container
          public void setServiceFactory(ServiceFactory myServiceFactory) {
              this.myServiceFactory = myServiceFactory;
          }

          public void someBusinessMethod() {
              // get a 'fresh', brand new MyService instance
              MyService service = this.myServiceFactory.getService();
              // use the service object to effect the business logic...
          }
      }

  By way of an example that looks up a bean by name, consider the following service locator interface. Again, note that this interface is not dependent on any Spring APIs.

      package a.b.c;

      public interface ServiceFactory {

          public MyService getService (String serviceName);
      }

  A sample config in an XML-based `BeanFactory` might look as follows:

      <beans>

         <!-- Prototype beans since we have state (both extend MyService) -->
         <bean id="specialService" class="a.b.c.SpecialService" singleton="false"/>
         <bean id="anotherService" class="a.b.c.AnotherService" singleton="false"/>

         <bean id="myServiceFactory"
                  class="org.springframework.beans.factory.config.ServiceLocatorFactoryBean">
           <property name="serviceLocatorInterface" value="a.b.c.ServiceFactory"/>
         </bean>

         <bean id="clientBean" class="a.b.c.MyClientBean">
           <property name="myServiceFactory" ref="myServiceFactory"/>
         </bean>

      </beans>

  The attendant `MyClientBean` class implementation might then look something like this:

      package a.b.c;

      public class MyClientBean {

          private ServiceFactory myServiceFactory;

          // actual implementation provided by the Spring container
          public void setServiceFactory(ServiceFactory myServiceFactory) {
              this.myServiceFactory = myServiceFactory;
          }

          public void someBusinessMethod() {
              // get a 'fresh', brand new MyService instance
              MyService service = this.myServiceFactory.getService("specialService");
              // use the service object to effect the business logic...
          }

          public void anotherBusinessMethod() {
              // get a 'fresh', brand new MyService instance
              MyService service = this.myServiceFactory.getService("anotherService");
              // use the service object to effect the business logic...
          }
      }

  See `ObjectFactoryCreatingFactoryBean` for an alternate approach.

  从以下版本开始:
    1.1.4
  作者:
    Colin Sampaleanu, Juergen Hoeller
  另请参阅:
    `setServiceLocatorInterface(java.lang.Class<?>)`, `setServiceMappings(java.util.Properties)`, `ObjectFactoryCreatingFactoryBean`

- - ### 构造器概要

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

  - ### 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.
    `protected Exception` | `createServiceLocatorException(Constructor<Exception> exceptionConstructor, BeansException cause)` Create a service locator exception for the given cause.
    `protected Constructor<Exception>` | `determineServiceLocatorExceptionConstructor(Class<? extends Exception> exceptionClass)` Determine the constructor to use for the given service locator exception class.
    `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.
    `boolean` | `isSingleton()` Is the object managed by this factory a singleton?
    `void` | `setBeanFactory(BeanFactory beanFactory)` Callback that supplies the owning factory to a bean instance.
    `void` | `setServiceLocatorExceptionClass(Class<? extends Exception> serviceLocatorExceptionClass)` Set the exception class that the service locator should throw if service lookup failed.
    `void` | `setServiceLocatorInterface(Class<?> interfaceType)` Set the service locator interface to use, which must have one or more methods with the signatures `MyType xxx()` or `MyType xxx(MyIdType id)` (typically, `MyService getService()` or `MyService getService(String id)`).
    `void` | `setServiceMappings(Properties serviceMappings)` Set mappings between service ids (passed into the service locator) and bean names (in the bean factory).

    - ### 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

    - #### ServiceLocatorFactoryBean

          public ServiceLocatorFactoryBean()

  - ### 方法详细资料

    - #### setServiceLocatorInterface

          public void setServiceLocatorInterface(Class<?> interfaceType)

      Set the service locator interface to use, which must have one or more methods with the signatures `MyType xxx()` or `MyType xxx(MyIdType id)` (typically, `MyService getService()` or `MyService getService(String id)`). See the `class-level Javadoc` for information on the semantics of such methods.

    - #### setServiceLocatorExceptionClass

          public void setServiceLocatorExceptionClass(Class<? extends Exception> serviceLocatorExceptionClass)

      Set the exception class that the service locator should throw if service lookup failed. The specified exception class must have a constructor with one of the following parameter types: `(String, Throwable)` or `(Throwable)` or `(String)`.

      If not specified, subclasses of Spring's BeansException will be thrown, for example NoSuchBeanDefinitionException. As those are unchecked, the caller does not need to handle them, so it might be acceptable that Spring exceptions get thrown as long as they are just handled generically.

      另请参阅:
        `determineServiceLocatorExceptionConstructor(java.lang.Class<? extends java.lang.Exception>)`, `createServiceLocatorException(java.lang.reflect.Constructor<java.lang.Exception>, org.springframework.beans.BeansException)`

    - #### setServiceMappings

          public void setServiceMappings(Properties serviceMappings)

      Set mappings between service ids (passed into the service locator) and bean names (in the bean factory). Service ids that are not defined here will be treated as bean names as-is.

      The empty string as service id key defines the mapping for `null` and empty string, and for factory methods without parameter. If not defined, a single matching bean will be retrieved from the bean factory.

      参数:
        `serviceMappings` - mappings between service ids and bean names, with service ids as keys as bean names as values

    - #### setBeanFactory

          public void setBeanFactory(BeanFactory beanFactory)
                              throws BeansException

      从接口复制的说明: `BeanFactoryAware`
      Callback that supplies the owning factory to a bean instance.

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

      指定者:
        `setBeanFactory` 在接口中 `BeanFactoryAware`
      参数:
        `beanFactory` - owning BeanFactory (never `null`). The bean can immediately call methods on the factory.
      抛出:
        `BeansException` - in case of initialization errors
      另请参阅:
        `BeanInitializationException`

    - #### afterPropertiesSet

          public void afterPropertiesSet()

      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`

    - #### determineServiceLocatorExceptionConstructor

          protected Constructor<Exception> determineServiceLocatorExceptionConstructor(Class<? extends Exception> exceptionClass)

      Determine the constructor to use for the given service locator exception class. Only called in case of a custom service locator exception.

      The default implementation looks for a constructor with one of the following parameter types: `(String, Throwable)` or `(Throwable)` or `(String)`.

      参数:
        `exceptionClass` - the exception class
      返回:
        the constructor to use
      另请参阅:
        `setServiceLocatorExceptionClass(java.lang.Class<? extends java.lang.Exception>)`

    - #### createServiceLocatorException

          protected Exception createServiceLocatorException(Constructor<Exception> exceptionConstructor,
                                                            BeansException cause)

      Create a service locator exception for the given cause. Only called in case of a custom service locator exception.

      The default implementation can handle all variations of message and exception arguments.

      参数:
        `exceptionConstructor` - the constructor to use
        `cause` - the cause of the service lookup failure
      返回:
        the service locator exception to throw
      另请参阅:
        `setServiceLocatorExceptionClass(java.lang.Class<? extends java.lang.Exception>)`

    - #### getObject

          @Nullable
          public Object getObject()

      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`)
      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()`