org.springframework.aop.target

Class AbstractLazyCreationTargetSource

java.lang.Object

org.springframework.aop.target.AbstractLazyCreationTargetSource

All Implemented Interfaces:

TargetClassAware, TargetSource

Direct Known Subclasses:

MBeanServerConnectionFactoryBean.JMXConnectorLazyInitTargetSource, MBeanServerConnectionFactoryBean.MBeanServerConnectionLazyInitTargetSource

public abstract class AbstractLazyCreationTargetSource
extends java.lang.Object
implements TargetSource

TargetSource implementation that will lazily create a user-managed object.

Creation of the lazy target object is controlled by the user by implementing the createObject() method. This TargetSource will invoke this method the first time the proxy is accessed.

Useful when you need to pass a reference to some dependency to an object but you don't actually want the dependency to be created until it is first used. A typical scenario for this is a connection to a remote resource.

Since:

1.2.4

Author:

Rob Harrop, Juergen Hoeller

See Also:

isInitialized(), createObject()

Field Summary

Fields

Modifier and Type	Field and Description
private java.lang.Object	lazyTarget The lazily initialized target object
protected Log	logger Logger available to subclasses

Constructor Summary

Constructors

Constructor and Description
AbstractLazyCreationTargetSource()

Method Summary

Methods

Modifier and Type	Method and Description
protected abstract java.lang.Object	createObject() Subclasses should implement this method to return the lazy initialized object.
java.lang.Object	getTarget() Returns the lazy-initialized target object, creating it on-the-fly if it doesn't exist already.
java.lang.Class<?>	getTargetClass() This default implementation returns null if the target is null (it is hasn't yet been initialized), or the target class if the target has already been initialized.
boolean	isInitialized() Return whether the lazy target object of this TargetSource has already been fetched.
boolean	isStatic() Will all calls to TargetSource.getTarget() return the same object?
void	releaseTarget(java.lang.Object target) Release the given target object obtained from the TargetSource.getTarget() method.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

logger

protected final Log logger

Logger available to subclasses

lazyTarget

private java.lang.Object lazyTarget

The lazily initialized target object

Constructor Detail

AbstractLazyCreationTargetSource

public AbstractLazyCreationTargetSource()

Method Detail

isInitialized

public boolean isInitialized()

Return whether the lazy target object of this TargetSource has already been fetched.

getTargetClass

public java.lang.Class<?> getTargetClass()

This default implementation returns null if the target is null (it is hasn't yet been initialized), or the target class if the target has already been initialized.

Subclasses may wish to override this method in order to provide a meaningful value when the target is still null.

Specified by:

getTargetClass in interface TargetClassAware

Specified by:

getTargetClass in interface TargetSource

Returns:

the type of targets returned by this TargetSource

See Also:

isInitialized()

isStatic

public boolean isStatic()

Description copied from interface: TargetSource

Will all calls to TargetSource.getTarget() return the same object?

In that case, there will be no need to invoke TargetSource.releaseTarget(Object), and the AOP framework can cache the return value of TargetSource.getTarget().

Specified by:

isStatic in interface TargetSource

Returns:

true if the target is immutable

See Also:

TargetSource.getTarget()

getTarget

public java.lang.Object getTarget()
                           throws java.lang.Exception

Returns the lazy-initialized target object, creating it on-the-fly if it doesn't exist already.

Specified by:

getTarget in interface TargetSource

Returns:

the target object, which contains the joinpoint

Throws:

java.lang.Exception - if the target object can't be resolved

See Also:

createObject()

releaseTarget

public void releaseTarget(java.lang.Object target)
                   throws java.lang.Exception

Description copied from interface: TargetSource

Release the given target object obtained from the TargetSource.getTarget() method.

Specified by:

releaseTarget in interface TargetSource

Parameters:

target - object obtained from a call to TargetSource.getTarget()

Throws:

java.lang.Exception - if the object can't be released

createObject

protected abstract java.lang.Object createObject()
                                          throws java.lang.Exception

Subclasses should implement this method to return the lazy initialized object. Called the first time the proxy is invoked.

Returns:

the created object

Throws:

java.lang.Exception - if creation failed