org.eclipse.persistence.internal.indirection

Class UnitOfWorkValueHolder

java.lang.Object

org.eclipse.persistence.internal.indirection.DatabaseValueHolder

org.eclipse.persistence.internal.indirection.UnitOfWorkValueHolder

All Implemented Interfaces:

java.io.Serializable, java.lang.Cloneable, ValueHolderInterface, WeavedAttributeValueHolderInterface, WrappingValueHolder

Direct Known Subclasses:

UnitOfWorkQueryValueHolder, UnitOfWorkTransformerValueHolder

public abstract class UnitOfWorkValueHolder
extends DatabaseValueHolder
implements WrappingValueHolder

A UnitOfWorkValueHolder is put in a clone object. It wraps the value holder in the original object to delay cloning the attribute in a unit of work until it is needed by the application. This value holder is used only in the unit of work.

Author:

Sati

See Also:

Serialized Form

Field Summary

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

shouldToStringInstantiate

Method Summary

Modifier and Type	Method and Description
abstract java.lang.Object	buildCloneFor(java.lang.Object originalAttributeValue) Clone the original attribute value.
DatabaseMapping	getMapping()
ValueHolderInterface	getWrappedValueHolder() Returns the valueholder that is wrapped by this ValueHolder
java.rmi.server.ObjID	getWrappedValueHolderRemoteID() returns wrapped ValueHolder ObjID if available
java.lang.Object	instantiateForUnitOfWorkValueHolder(UnitOfWorkValueHolder unitOfWorkValueHolder) Triggers UnitOfWork valueholders directly without triggering the wrapped valueholder (this).
boolean	isEasilyInstantiated() INTERNAL: Answers if this valueholder is easy to instantiate.
boolean	isPessimisticLockingValueHolder() INTERNAL: Answers if this valueholder is a pessimistic locking one.
boolean	isSerializedRemoteUnitOfWorkValueHolder() Used to determine if this is a remote uow value holder that was serialized to the server.
void	releaseWrappedValueHolder(AbstractSession targetSession) Releases a wrapped valueholder privately owned by a particular unit of work.
void	setBackupValueHolder(ValueHolderInterface backupValueHolder)
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, getValue, isCoordinatedWithProperty, isInstantiated, isNewlyWeavedValueHolder, postInstantiate, privilegedSetValue, setInstantiated, setIsCoordinatedWithProperty, setIsNewlyWeavedValueHolder, setRow, setSession, setUninstantiated, setValue, toString

Methods inherited from class java.lang.Object

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

Method Detail

buildCloneFor

public abstract java.lang.Object buildCloneFor(java.lang.Object originalAttributeValue)

Clone the original attribute value.

getMapping

public DatabaseMapping getMapping()

isEasilyInstantiated

public boolean isEasilyInstantiated()

INTERNAL: Answers if this valueholder is easy to instantiate.

Overrides:

isEasilyInstantiated in class DatabaseValueHolder

Returns:

true if getValue() won't trigger a database read.

isPessimisticLockingValueHolder

public boolean isPessimisticLockingValueHolder()

INTERNAL: 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 instantatiated all fields can not be reset.

Specified by:

isPessimisticLockingValueHolder in class DatabaseValueHolder

getWrappedValueHolder

public ValueHolderInterface getWrappedValueHolder()

Description copied from interface: WrappingValueHolder

Returns the valueholder that is wrapped by this ValueHolder

Specified by:

getWrappedValueHolder in interface WrappingValueHolder

Overrides:

getWrappedValueHolder in class DatabaseValueHolder

getWrappedValueHolderRemoteID

public java.rmi.server.ObjID getWrappedValueHolderRemoteID()

returns wrapped ValueHolder ObjID if available

isSerializedRemoteUnitOfWorkValueHolder

public boolean isSerializedRemoteUnitOfWorkValueHolder()

Used to determine if this is a remote uow value holder that was serialized to the server. It has no reference to its wrapper value holder, so must find its original object to be able to instantiate.

Overrides:

isSerializedRemoteUnitOfWorkValueHolder in class DatabaseValueHolder

instantiateForUnitOfWorkValueHolder

public java.lang.Object instantiateForUnitOfWorkValueHolder(UnitOfWorkValueHolder 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.

Specified by:

instantiateForUnitOfWorkValueHolder in class DatabaseValueHolder

releaseWrappedValueHolder

public void releaseWrappedValueHolder(AbstractSession targetSession)

Releases a wrapped valueholder privately owned by a particular unit of work.

When unit of work clones are built directly from rows no object in the shared cache points to this valueholder, so it can store the unit of work as its session. However once that UnitOfWork commits and the valueholder is merged into the shared cache, the session needs to be reset to the root session, ie. the server session.

Overrides:

releaseWrappedValueHolder in class DatabaseValueHolder

setBackupValueHolder

public void setBackupValueHolder(ValueHolderInterface backupValueHolder)

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

Overrides:

shouldAllowInstantiationDeferral in class DatabaseValueHolder