org.springframework.beans.factory.config
Class MethodInvokingFactoryBean

java.lang.Object
  org.springframework.util.MethodInvoker
      org.springframework.beans.support.ArgumentConvertingMethodInvoker
          org.springframework.beans.factory.config.MethodInvokingFactoryBean

All Implemented Interfaces:

Aware, BeanClassLoaderAware, BeanFactoryAware, FactoryBean<Object>, InitializingBean

public class MethodInvokingFactoryBean
extends ArgumentConvertingMethodInvoker
implements FactoryBean<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.
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.
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 Class	resolveClassName(String className) Resolve the given class name into a Class.
void	setBeanClassLoader(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<Object>

Returns:

whether the exposed object is a singleton

See Also:

FactoryBean.getObject(), SmartFactoryBean.isPrototype()

setBeanClassLoader

public void setBeanClassLoader(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 Class resolveClassName(String className)
                          throws 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:

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 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:

Exception - in the event of misconfiguration (such as failure to set an essential property) or if initialization fails.

getObject

public Object getObject()
                 throws 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<Object>

Returns:

an instance of the bean (can be null)

Throws:

Exception - in case of creation errors

See Also:

FactoryBeanNotInitializedException

getObjectType

public Class<?> getObjectType()

Return the type of object that this FactoryBean creates, or null if not known in advance.

Specified by:

getObjectType in interface FactoryBean<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)