Spring Framework

org.springframework.beans.factory.config
Class MethodInvokingFactoryBean

java.lang.Object
  extended by org.springframework.util.MethodInvoker
      extended by org.springframework.beans.support.ArgumentConvertingMethodInvoker
          extended by org.springframework.beans.factory.config.MethodInvokingFactoryBean
All Implemented Interfaces:
Aware, BeanClassLoaderAware, BeanFactoryAware, FactoryBean<java.lang.Object>, InitializingBean

public class MethodInvokingFactoryBean
extends ArgumentConvertingMethodInvoker
implements FactoryBean<java.lang.Object>, BeanClassLoaderAware, BeanFactoryAware, InitializingBean

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.

A static target 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</value></property>
 </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</value></property>
   <property name="targetMethod"><value>getProperties</value></property>
 </bean>

 <bean id="javaVersion" class="org.springframework.beans.factory.config.MethodInvokingFactoryBean">
   <property name="targetObject"><ref local="sysProps"/></property>
   <property name="targetMethod"><value>getProperty</value></property>
   <property name="arguments">
     <list>
       <value>java.version</value>
     </list>
   </property>
 </bean>

Since:
21.11.2003
Author:
Colin Sampaleanu, Juergen Hoeller

Constructor Summary
MethodInvokingFactoryBean()
           
 
Method Summary
 void afterPropertiesSet()
          Invoked by a BeanFactory after it has set all bean properties supplied (and satisfied BeanFactoryAware and ApplicationContextAware).
protected  TypeConverter getDefaultTypeConverter()
          Obtain the TypeConverter from the BeanFactory that this bean runs in, if possible.
 java.lang.Object getObject()
          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.
 java.lang.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? That is, will FactoryBean.getObject() always return the same object (a reference that can be cached)?
protected  java.lang.Class resolveClassName(java.lang.String className)
          Resolve the given class name into a Class.
 void setBeanClassLoader(java.lang.ClassLoader classLoader)
          Callback that supplies the bean class loader to a bean instance.
 void setBeanFactory(BeanFactory beanFactory)
          Callback that supplies the owning factory to a bean instance.
 void setSingleton(boolean singleton)
          Set if a singleton should be created, or a new object on each request else.
 
Methods inherited from class org.springframework.beans.support.ArgumentConvertingMethodInvoker
doFindMatchingMethod, findMatchingMethod, getTypeConverter, registerCustomEditor, setTypeConverter
 
Methods inherited from class org.springframework.util.MethodInvoker
getArguments, getPreparedMethod, getTargetClass, getTargetMethod, getTargetObject, getTypeDifferenceWeight, invoke, isPrepared, prepare, setArguments, setStaticMethod, setTargetClass, setTargetMethod, setTargetObject
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

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 request else. Default is "true".


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.

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

setBeanClassLoader

public void setBeanClassLoader(java.lang.ClassLoader classLoader)
Description copied from interface: 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.

Specified by:
setBeanClassLoader in interface BeanClassLoaderAware
Parameters:
classLoader - the owning class loader; may be null in which case a default ClassLoader must be used, for example the ClassLoader obtained via ClassUtils.getDefaultClassLoader()

resolveClassName

protected java.lang.Class resolveClassName(java.lang.String className)
                                    throws java.lang.ClassNotFoundException
Description copied from class: MethodInvoker
Resolve the given class name into a Class.

The default implementations uses ClassUtils.forName, using the thread context class loader.

Overrides:
resolveClassName in class MethodInvoker
Parameters:
className - the class name to resolve
Returns:
the resolved Class
Throws:
java.lang.ClassNotFoundException - if the class name was invalid

setBeanFactory

public void setBeanFactory(BeanFactory beanFactory)
Description copied from interface: 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.

Specified by:
setBeanFactory in interface BeanFactoryAware
Parameters:
beanFactory - owning BeanFactory (never null). The bean can immediately call methods on the factory.
See Also:
BeanInitializationException

getDefaultTypeConverter

protected TypeConverter getDefaultTypeConverter()
Obtain the TypeConverter from the BeanFactory that this bean runs in, if possible.

Overrides:
getDefaultTypeConverter in class ArgumentConvertingMethodInvoker
See Also:
ConfigurableBeanFactory.getTypeConverter()

afterPropertiesSet

public void afterPropertiesSet()
                        throws java.lang.Exception
Description copied from interface: InitializingBean
Invoked by a BeanFactory after it has set all bean properties supplied (and satisfied BeanFactoryAware and ApplicationContextAware).

This method allows the bean instance to perform initialization only possible when all bean properties have been set and to throw an exception in the event of misconfiguration.

Specified by:
afterPropertiesSet in interface InitializingBean
Throws:
java.lang.Exception - in the event of misconfiguration (such as failure to set an essential property) or if initialization fails.

getObject

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)

Spring Framework