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 java.lang.Object
Concrete CallbackContext
implementation that is specific to
intercepted get() operations. Methods annotated with 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.
Methods inherited from class java.lang.Object |
equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
setResultForCurrentElement
public void setResultForCurrentElement(Entity entity)
- Set the
Entity
that will be associated with the Key
returned by 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:
java.lang.IllegalArgumentException
- If the key of the provided entity is not
equal to the key returned by getCurrentElement()
.
getElements
public java.util.List<T> getElements()
- Specified by:
getElements
in interface CallbackContext<T>
- Returns:
- An unmodifiable view of the elements involved in the operation
that triggered the callback..
getCurrentTransaction
public Transaction getCurrentTransaction()
- Specified by:
getCurrentTransaction
in interface CallbackContext<T>
- Returns:
- The current transaction, or
null
if there is no current
transaction.
getCurrentIndex
public int getCurrentIndex()
- Specified by:
getCurrentIndex
in interface CallbackContext<T>
- Returns:
- The index in the result of
CallbackContext.getElements()
of the element
for which the callback has been invoked.
getCurrentElement
public T getCurrentElement()
- Specified by:
getCurrentElement
in interface CallbackContext<T>
- Returns:
- The element for which the callback has been invoked. Shortcut
for
getElements().getCurrentIndex()
.