org.springframework.beans.factory.config

Class MethodInvokingFactoryBean

java.lang.Object

org.springframework.util.MethodInvoker

org.springframework.beans.support.ArgumentConvertingMethodInvoker

org.springframework.beans.factory.config.MethodInvokingBean

org.springframework.beans.factory.config.MethodInvokingFactoryBean

All Implemented Interfaces:

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

public class MethodInvokingFactoryBean
extends MethodInvokingBean
implements FactoryBean<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

Field Summary

Fields inherited from class org.springframework.util.MethodInvoker

targetClass

Fields inherited from interface org.springframework.beans.factory.FactoryBean

OBJECT_TYPE_ATTRIBUTE

Constructor Summary

Constructors

Constructor and Description
MethodInvokingFactoryBean()

Method Summary

Modifier and Type	Method and Description
void	afterPropertiesSet() Invoked by the containing BeanFactory after it has set all bean properties and satisfied BeanFactoryAware, ApplicationContextAware etc.
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)?
void	setSingleton(boolean singleton) Set if a singleton should be created, or a new object on each getObject() request otherwise.

Methods inherited from class org.springframework.beans.factory.config.MethodInvokingBean

getDefaultTypeConverter, invokeWithTargetException, resolveClassName, setBeanClassLoader, setBeanFactory

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 getObject() request otherwise. Default is "true".

afterPropertiesSet

public void afterPropertiesSet()
                        throws 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:

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 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<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<Object>

Returns:

whether the exposed object is a singleton

See Also:

FactoryBean.getObject(), SmartFactoryBean.isPrototype()