org.eclipse.persistence.internal.indirection

Class DatabaseValueHolder

java.lang.Object

org.eclipse.persistence.internal.indirection.DatabaseValueHolder

All Implemented Interfaces:

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

Direct Known Subclasses:

BackupValueHolder, CacheBasedValueHolder, ProtectedValueHolder, QueryBasedValueHolder, RemoteValueHolder, TransformerBasedValueHolder, UnitOfWorkValueHolder

public abstract class DatabaseValueHolder
extends java.lang.Object
implements WeavedAttributeValueHolderInterface, java.lang.Cloneable, java.io.Serializable

DatabaseValueHolder wraps a database-stored object and implements behavior to access it. The object is read only once from database after which is cached for faster access.

Author:

Dorin Sandu

See Also:

ValueHolderInterface, Serialized Form

Field Summary

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

shouldToStringInstantiate

Constructor Summary

Constructors

Constructor and Description
DatabaseValueHolder()

Method Summary

Modifier and Type	Method and Description
java.lang.Object	clone() PUBLIC: Copy the value holder (but not its' reference, shallow).
AbstractRecord	getRow() Return the row.
AbstractSession	getSession() Return the session.
java.lang.Object	getValue() Return the object.
java.lang.Object	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.
ValueHolderInterface	getWrappedValueHolder()
abstract java.lang.Object	instantiateForUnitOfWorkValueHolder(UnitOfWorkValueHolder unitOfWorkValueHolder) Triggers UnitOfWork valueholders directly without triggering the wrapped valueholder (this).
boolean	isCoordinatedWithProperty() This method is used as part of the implementation of WeavedAttributeValueHolderInterface It is used to check whether a valueholder that has been weaved into a class is coordinated with the underlying property
boolean	isEasilyInstantiated() INTERNAL: Answers if this valueholder is easy to instantiate.
boolean	isInstantiated() Return a boolean indicating whether the object has been read from the database or not.
boolean	isNewlyWeavedValueHolder() This method is used as part of the implementation of WeavedAttributeValueHolderInterface.
abstract boolean	isPessimisticLockingValueHolder() 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	postInstantiate() INTERNAL: Run any extra code required after the valueholder instantiates
void	privilegedSetValue(java.lang.Object value) Set the object.
void	releaseWrappedValueHolder(AbstractSession targetSession) Releases a wrapped valueholder privately owned by a particular unit of work.
void	setInstantiated() Set the instantiated flag to true.
void	setIsCoordinatedWithProperty(boolean coordinated) This method is used as part of the implementation of WeavedAttributeValueHolderInterface It is used internally by EclipseLink to set whether a valueholder that has been weaved into a class is coordinated with the underlying property
void	setIsNewlyWeavedValueHolder(boolean isNew) This method is used as part of the implementation of WeavedAttributeValueHolderInterface A DatabaseValueHolder is set up by EclipseLink and will never be a newly weaved valueholder As a result, this method is stubbed out.
void	setRow(AbstractRecord row) Set the row.
void	setSession(AbstractSession session) Set the session.
void	setUninstantiated() Set the instantiated flag to false.
void	setValue(java.lang.Object value) Set the object.
boolean	shouldAllowInstantiationDeferral() INTERNAL: Return if add/remove should trigger instantiation or avoid.
java.lang.String	toString()

Methods inherited from class java.lang.Object

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

Constructor Detail

DatabaseValueHolder

public DatabaseValueHolder()

Method Detail

clone

public java.lang.Object clone()

Description copied from interface: ValueHolderInterface

PUBLIC: Copy the value holder (but not its' reference, shallow).

Specified by:

clone in interface ValueHolderInterface

Overrides:

clone in class java.lang.Object

getRow

public AbstractRecord getRow()

Return the row.

getSession

public AbstractSession getSession()

Return the session.

getWrappedValueHolder

public ValueHolderInterface getWrappedValueHolder()

getValue

public java.lang.Object getValue()

Return the object.

Specified by:

getValue in interface ValueHolderInterface

getValue

public java.lang.Object 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.

instantiateForUnitOfWorkValueHolder

public abstract 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. Note: Implementations of this method are not necessarily thread-safe. They must be used in a synchronized manner

isCoordinatedWithProperty

public boolean isCoordinatedWithProperty()

This method is used as part of the implementation of WeavedAttributeValueHolderInterface It is used to check whether a valueholder that has been weaved into a class is coordinated with the underlying property

Specified by:

isCoordinatedWithProperty in interface WeavedAttributeValueHolderInterface

Returns:

isNewlyWeavedValueHolder

public boolean isNewlyWeavedValueHolder()

This method is used as part of the implementation of WeavedAttributeValueHolderInterface. A DatabaseValueHolder is set up by TopLink and will never be a newly weaved valueholder. As a result, this method is stubbed out.

Specified by:

isNewlyWeavedValueHolder in interface WeavedAttributeValueHolderInterface

Returns:

isEasilyInstantiated

public boolean isEasilyInstantiated()

INTERNAL: Answers if this valueholder is easy to instantiate.

Returns:

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

isInstantiated

public boolean isInstantiated()

Return a boolean indicating whether the object has been read from the database or not.

Specified by:

isInstantiated in interface ValueHolderInterface

isPessimisticLockingValueHolder

public abstract boolean isPessimisticLockingValueHolder()

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

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.

postInstantiate

public void postInstantiate()

INTERNAL: Run any extra code required after the valueholder instantiates

See Also:

QueryBasedValueHolder

privilegedSetValue

public void privilegedSetValue(java.lang.Object value)

Set the object. This is used only by the privileged methods. One must be very careful in using this method.

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.

setIsCoordinatedWithProperty

public void setIsCoordinatedWithProperty(boolean coordinated)

This method is used as part of the implementation of WeavedAttributeValueHolderInterface It is used internally by EclipseLink to set whether a valueholder that has been weaved into a class is coordinated with the underlying property

Specified by:

setIsCoordinatedWithProperty in interface WeavedAttributeValueHolderInterface

setIsNewlyWeavedValueHolder

public void setIsNewlyWeavedValueHolder(boolean isNew)

This method is used as part of the implementation of WeavedAttributeValueHolderInterface A DatabaseValueHolder is set up by EclipseLink and will never be a newly weaved valueholder As a result, this method is stubbed out.

Specified by:

setIsNewlyWeavedValueHolder in interface WeavedAttributeValueHolderInterface

setInstantiated

public void setInstantiated()

Set the instantiated flag to true.

setRow

public void setRow(AbstractRecord row)

Set the row.

setSession

public void setSession(AbstractSession session)

Set the session.

setUninstantiated

public void setUninstantiated()

Set the instantiated flag to false.

setValue

public void setValue(java.lang.Object value)

Set the object.

Specified by:

setValue in interface ValueHolderInterface

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

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object