org.springframework.aop.target
Class AbstractLazyCreationTargetSource

java.lang.Object
  org.springframework.aop.target.AbstractLazyCreationTargetSource

All Implemented Interfaces:

TargetSource

public abstract class AbstractLazyCreationTargetSource
extends Object
implements TargetSource

TargetSource 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:

createObject()

Field Summary

protected Log

logger Log instance for this class and sub-classes

Constructor Summary

AbstractLazyCreationTargetSource()

Method Summary

protected abstract Object	createObject() Sub-classes should implement this method to return the lazy initialized object.
Object	getTarget() Returns the lazy-initialized target object, creating it if it doesn't exist.
Class	getTargetClass() 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(Object target) No need to release target - no op.

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

Log instance for this class and sub-classes

Constructor Detail

AbstractLazyCreationTargetSource

public AbstractLazyCreationTargetSource()

Method Detail

getTargetClass

public Class getTargetClass()

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 to provide more meaningful values when the target is still null.

Specified by:

getTargetClass in interface TargetSource

Returns:

the type of targets returned by this TargetSource

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 Object getTarget()
                 throws Exception

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

Specified by:

getTarget in interface TargetSource

Returns:

the target object, which contains the joinpoint

Throws:

Exception - if the target object can't be resolved

See Also:

createObject()

isInitialized

public boolean isInitialized()

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

releaseTarget

public void releaseTarget(Object target)
                   throws Exception

No need to release target - no op.

Specified by:

releaseTarget in interface TargetSource

Parameters:

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

Throws:

Exception - if the object can't be released

createObject

protected abstract Object createObject()
                                throws Exception

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

Throws:

Exception - if creation failed