Module org.eclipse.persistence.core

Package org.eclipse.persistence.internal.indirection

Class CacheBasedValueHolder<T>

java.lang.Object

org.eclipse.persistence.internal.indirection.DatabaseValueHolder<T>

org.eclipse.persistence.internal.indirection.CacheBasedValueHolder<T>

All Implemented Interfaces:

Serializable, Cloneable, ValueHolderInterface<T>, WeavedAttributeValueHolderInterface<T>

public class CacheBasedValueHolder<T>
extends DatabaseValueHolder<T>

Purpose: In certain cases the contents of a relationship may be retrievable from a cache. This ValueHolder instance provides the mechanism to store a cached relationship and to load that relationship from a cache. This functionality requires that the persistent identities of the targets can be collected as database type foreign key queries are unavailable.

Since:

EclipseLink 1.1

Author:

gyorke

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field	Description
protected ForeignReferenceMapping	mapping
protected Object[]	references
protected boolean	shouldAllowInstantiationDeferral	Setting to force the instantiation of the Collection on modification

Fields inherited from class org.eclipse.persistence.internal.indirection.DatabaseValueHolder

isCoordinatedWithProperty, isInstantiated, row, session, value

Fields inherited from interface org.eclipse.persistence.indirection.ValueHolderInterface

shouldToStringInstantiate

Constructor Summary

Constructors

Constructor	Description
CacheBasedValueHolder(Object[] pks, AbstractRecord foreignKeys, AbstractSession session, ForeignReferenceMapping mapping)

Method Summary

Modifier and Type	Method	Description
Object[]	getCachedPKs()
T	getValue(UnitOfWorkImpl uow)	Process against the UOW and attempt to load a local copy before going to the shared cache If null is returned then the calling UOW will instantiate as normal.
protected T	instantiate()	Instantiate the object.
protected T	instantiate(AbstractSession localSession)
T	instantiateForUnitOfWorkValueHolder(UnitOfWorkValueHolder<T> unitOfWorkValueHolder)	Triggers UnitOfWork valueholders directly without triggering the wrapped valueholder (this).
boolean	isPessimisticLockingValueHolder()	Answers if this valueholder is a pessimistic locking one.
void	setShouldAllowInstantiationDeferral(boolean shouldAllowInstantiationDeferral)	Set if instantiation deferral on modification should be available.
boolean	shouldAllowInstantiationDeferral()	INTERNAL: Return if add/remove should trigger instantiation or avoid.

Methods inherited from class org.eclipse.persistence.internal.indirection.DatabaseValueHolder

clone, getRow, getSession, getValue, getWrappedValueHolder, isCoordinatedWithProperty, isEasilyInstantiated, isInstantiated, isNewlyWeavedValueHolder, isSerializedRemoteUnitOfWorkValueHolder, isTransactionalValueHolder, postInstantiate, privilegedSetValue, releaseWrappedValueHolder, resetFields, setInstantiated, setIsCoordinatedWithProperty, setIsNewlyWeavedValueHolder, setRow, setSession, setUninstantiated, setValue, toString

Methods inherited from class java.lang.Object

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

Field Detail

mapping

protected transient ForeignReferenceMapping mapping

references

protected Object[] references

shouldAllowInstantiationDeferral

protected boolean shouldAllowInstantiationDeferral

Setting to force the instantiation of the Collection on modification

Constructor Detail

CacheBasedValueHolder

public CacheBasedValueHolder(Object[] pks,
                             AbstractRecord foreignKeys,
                             AbstractSession session,
                             ForeignReferenceMapping mapping)

Method Detail

getCachedPKs

public Object[] getCachedPKs()

getValue

public T getValue(UnitOfWorkImpl uow)

Process against the UOW and attempt to load a local copy before going to the shared cache If null is returned then the calling UOW will instantiate as normal.

Overrides:

getValue in class DatabaseValueHolder<T>

instantiate

protected T instantiate()
                 throws DatabaseException

Description copied from class: DatabaseValueHolder

Instantiate the object.

Specified by:

instantiate in class DatabaseValueHolder<T>

Throws:

DatabaseException

instantiate

protected T instantiate(AbstractSession localSession)
                 throws DatabaseException

Throws:

DatabaseException

instantiateForUnitOfWorkValueHolder

public T instantiateForUnitOfWorkValueHolder(UnitOfWorkValueHolder<T> unitOfWorkValueHolder)

Triggers UnitOfWork valueholders directly without triggering the wrapped valueholder (this).

When in transaction and/or for pessimistic locking the UnitOfWorkValueHolder needs to be triggered directly without triggering the wrapped valueholder. However only the wrapped valueholder knows how to trigger the indirection, i.e. it may be a batchValueHolder, and it stores all the info like the row and the query. Note: This method is not thread-safe. It must be used in a synchronized manner

Specified by:

instantiateForUnitOfWorkValueHolder in class DatabaseValueHolder<T>

isPessimisticLockingValueHolder

public boolean isPessimisticLockingValueHolder()

Description copied from class: DatabaseValueHolder

Answers if this valueholder is a pessimistic locking one. Such valueholders are special in that they can be triggered multiple times by different UnitsOfWork. Each time a lock query will be issued. Hence even if instantiated it may have to be instantiated again, and once instantiated all fields can not be reset. Note: Implementations of this method are not necessarily thread-safe. They must be used in a synchronizaed manner

Specified by:

isPessimisticLockingValueHolder in class DatabaseValueHolder<T>

setShouldAllowInstantiationDeferral

public void setShouldAllowInstantiationDeferral(boolean shouldAllowInstantiationDeferral)

Set if instantiation deferral on modification should be available.

shouldAllowInstantiationDeferral

public boolean shouldAllowInstantiationDeferral()

INTERNAL: Return if add/remove should trigger instantiation or avoid. Current instantiation is avoided is using change tracking.

Specified by:

shouldAllowInstantiationDeferral in interface WeavedAttributeValueHolderInterface<T>

Overrides:

shouldAllowInstantiationDeferral in class DatabaseValueHolder<T>