org.springframework.beans.factory.config

Class MethodInvokingFactoryBean

  • All Implemented Interfaces:
    Aware, BeanClassLoaderAware, BeanFactoryAware, FactoryBean<java.lang.Object>, InitializingBean


    public class MethodInvokingFactoryBean
    extends MethodInvokingBean
    implements FactoryBean<java.lang.Object>
    FactoryBean which returns a value which is the result of a static or instance method invocation. For most use cases it is better to just use the container's built-in factory method support for the same purpose, since that is smarter at converting arguments. This factory bean is still useful though when you need to call a method which doesn't return any value (for example, a static class method to force some sort of initialization to happen). This use case is not supported by factory methods, since a return value is needed to obtain the bean instance.

    Note that as it is expected to be used mostly for accessing factory methods, this factory by default operates in a singleton fashion. The first request to getObject() by the owning bean factory will cause a method invocation, whose return value will be cached for subsequent requests. An internal singleton property may be set to "false", to cause this factory to invoke the target method each time it is asked for an object.

    NOTE: If your target method does not produce a result to expose, consider MethodInvokingBean instead, which avoids the type determination and lifecycle limitations that this MethodInvokingFactoryBean comes with.

    This invoker supports any kind of target method. A static method may be specified by setting the targetMethod property to a String representing the static method name, with targetClass specifying the Class that the static method is defined on. Alternatively, a target instance method may be specified, by setting the targetObject property as the target object, and the targetMethod property as the name of the method to call on that target object. Arguments for the method invocation may be specified by setting the arguments property.

    This class depends on afterPropertiesSet() being called once all properties have been set, as per the InitializingBean contract.

    An example (in an XML based bean factory definition) of a bean definition which uses this class to call a static factory method:

     <bean id="myObject" class="org.springframework.beans.factory.config.MethodInvokingFactoryBean">
       <property name="staticMethod" value="com.whatever.MyClassFactory.getInstance"/>
     </bean>

    An example of calling a static method then an instance method to get at a Java system property. Somewhat verbose, but it works.

     <bean id="sysProps" class="org.springframework.beans.factory.config.MethodInvokingFactoryBean">
       <property name="targetClass" value="java.lang.System"/>
       <property name="targetMethod" value="getProperties"/>
     </bean>
    
     <bean id="javaVersion" class="org.springframework.beans.factory.config.MethodInvokingFactoryBean">
       <property name="targetObject" ref="sysProps"/>
       <property name="targetMethod" value="getProperty"/>
       <property name="arguments" value="java.version"/>
     </bean>
    Since:
    21.11.2003
    Author:
    Colin Sampaleanu, Juergen Hoeller
    See Also:
    MethodInvokingBean, MethodInvoker
    • Constructor Detail

      • MethodInvokingFactoryBean

        public MethodInvokingFactoryBean()
    • Method Detail

      • setSingleton

        public void setSingleton(boolean singleton)
        Set if a singleton should be created, or a new object on each getObject() request otherwise. Default is "true".
      • afterPropertiesSet

        public void afterPropertiesSet()
                                throws java.lang.Exception
        Description copied from interface: 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.

        Specified by:
        afterPropertiesSet in interface InitializingBean
        Overrides:
        afterPropertiesSet in class MethodInvokingBean
        Throws:
        java.lang.Exception - in the event of misconfiguration (such as failure to set an essential property) or if initialization fails for any other reason
      • getObject

        @Nullable
        public java.lang.Object getObject()
                                             throws java.lang.Exception
        Returns the same value each time if the singleton property is set to "true", otherwise returns the value returned from invoking the specified method on the fly.
        Specified by:
        getObject in interface FactoryBean<java.lang.Object>
        Returns:
        an instance of the bean (can be null)
        Throws:
        java.lang.Exception - in case of creation errors
        See Also:
        FactoryBeanNotInitializedException
      • getObjectType

        public java.lang.Class<?> getObjectType()
        Return the type of object that this FactoryBean creates, or null if not known in advance.
        Specified by:
        getObjectType in interface FactoryBean<java.lang.Object>
        Returns:
        the type of object that this FactoryBean creates, or null if not known at the time of the call
        See Also:
        ListableBeanFactory.getBeansOfType(java.lang.Class<T>)
      • isSingleton

        public boolean isSingleton()
        Description copied from interface: 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.

        Specified by:
        isSingleton in interface FactoryBean<java.lang.Object>
        Returns:
        whether the exposed object is a singleton
        See Also:
        FactoryBean.getObject(), SmartFactoryBean.isPrototype()