Package com.google.appengine.api.datastore

Class PreGetContext

java.lang.Object

com.google.appengine.api.datastore.PreGetContext

All Implemented Interfaces:

CallbackContext<Key>

public final class PreGetContext
extends Object

Concrete CallbackContext implementation that is specific to intercepted get() operations. Methods annotated with PreGet that receive instances of this class may modify the result of the get() operation by calling setResultForCurrentElement(Entity). Keys that receive results via this method will not be fetched from the datastore. This is an effective way to inject cached results.

Method Summary

Modifier and Type	Method	Description
Key	getCurrentElement()	Returns the element for which the callback has been invoked.
int	getCurrentIndex()	Returns the index in the result of CallbackContext.getElements() of the element for which the callback has been invoked.
Transaction	getCurrentTransaction()	Returns the current transaction, or null if there is no current transaction.
List<Key>	getElements()	Returns an unmodifiable view of the elements involved in the operation that triggered the callback..
void	setResultForCurrentElement(Entity entity)	Set the Entity that will be associated with the Key returned by CallbackContext.getCurrentElement() in the result of the get() operation.
String	toString()

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Method Details

setResultForCurrentElement

public void setResultForCurrentElement(Entity entity)

Set the Entity that will be associated with the Key returned by CallbackContext.getCurrentElement() in the result of the get() operation. This will prevent the get() operation from fetching the Entity from the datastore. This is an effective way to inject cached results.

Parameters:

entity - The entity to provide as the result for the current element.

Throws:

IllegalArgumentException - If the key of the provided entity is not equal to the key returned by CallbackContext.getCurrentElement().

getElements

public List<Key> getElements()

Description copied from interface: CallbackContext

Returns an unmodifiable view of the elements involved in the operation that triggered the callback..

Specified by:

getElements in interface CallbackContext<T>

getCurrentTransaction

public Transaction getCurrentTransaction()

Description copied from interface: CallbackContext

Returns the current transaction, or null if there is no current transaction.

Specified by:

getCurrentTransaction in interface CallbackContext<T>

getCurrentIndex

public int getCurrentIndex()

Description copied from interface: CallbackContext

Returns the index in the result of CallbackContext.getElements() of the element for which the callback has been invoked.

Specified by:

getCurrentIndex in interface CallbackContext<T>

getCurrentElement

public Key getCurrentElement()

Description copied from interface: CallbackContext

Returns the element for which the callback has been invoked. Shortcut for getElements().getCurrentIndex().

Specified by:

getCurrentElement in interface CallbackContext<T>

toString

public String toString()

Overrides:

toString in class Object