AbstractLazyCreationTargetSource (Spring Framework API 2.1) - Spring Framework 2.1.0 API 文档英文版

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org.springframework.aop.target
Class AbstractLazyCreationTargetSource

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

All Implemented Interfaces:: TargetClassAware, TargetSource

public abstract class AbstractLazyCreationTargetSource
extends Object
implements TargetSource
extends 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

protected Log logger
          Logger available to subclasses

Constructor Summary

AbstractLazyCreationTargetSource()


Method Summary

protected abstract Object createObject()
          Subclasses should implement this method to return the lazy initialized object.

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

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(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 Summary
`protected Log`	`logger` Logger available to subclasses

Constructor Summary
`AbstractLazyCreationTargetSource()`

Method Summary
`protected abstract Object`	`createObject()` Subclasses should implement this method to return the lazy initialized object.
`Object`	`getTarget()` Returns the lazy-initialized target object, creating it on-the-fly if it doesn't exist already.
`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(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

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 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 Object getTarget()
                 throws 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:: Exception - if the target object can't be resolved
See Also:: createObject()

releaseTarget

public void releaseTarget(Object target)
                   throws Exception