Module org.eclipse.persistence.core

Package org.eclipse.persistence.internal.indirection

Class TransformerBasedValueHolder<T>

java.lang.Object

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

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

All Implemented Interfaces:

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

public class TransformerBasedValueHolder<T>
extends DatabaseValueHolder<T>

Since:

release specific (what release of product did this appear in) This class is to replace the MethodBasedValueHolder for TransformationMappings Holds on to an AttributeTransformer and uses it to generate the attribute value when triggered. That Transformer may be a MethodBasedAttributeTransformer or a user defined implementation.

Version:

$Header: TransformerBasedValueHolder.java 30-aug-2006.11:32:36 gyorke Exp $

See Also:

• Serialized Form

Field Summary

Fields

Modifier and Type	Field	Description
protected Object	object	Stores the object which owns this attribute.
protected AttributeTransformer	transformer	Stores the method to be executed.

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
TransformerBasedValueHolder(AttributeTransformer theTransformer, Object theObject, AbstractRecord theRow, AbstractSession theSession)	Initialize the method-based value holder.

Method Summary

Modifier and Type	Method	Description
protected Object	getObject()	Return the receiver.
protected AttributeTransformer	getTransformer()	Return the method.
protected T	instantiate()	Instantiate the object by executing the method on the transformer.
protected T	instantiate(Object object, AbstractSession session)
T	instantiateForUnitOfWorkValueHolder(UnitOfWorkValueHolder<T> unitOfWorkValueHolder)	Triggers UnitOfWork valueholders directly without triggering the wrapped valueholder (this).
boolean	isPessimisticLockingValueHolder()	INTERNAL: Answers if this valueholder is a pessimistic locking one.
protected void	setObject(Object theObject)	Set the receiver.
protected void	setTransformer(AttributeTransformer theTransformer)	Set the transformer.

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

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

Methods inherited from class java.lang.Object

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

Field Details

transformer

protected transient AttributeTransformer transformer

Stores the method to be executed. The method can take one (the row) or two parameters (the row and session).

object

protected transient Object object

Stores the object which owns this attribute.

Constructor Details

TransformerBasedValueHolder

public TransformerBasedValueHolder(AttributeTransformer theTransformer,
 Object theObject,
 AbstractRecord theRow,
 AbstractSession theSession)

Initialize the method-based value holder.

Parameters:

theTransformer - The method that returns the object when executed.

theObject - the Object which owns this attribute.

theRow - The row representation of the object.

theSession - The session to the database that stores the object.

Method Details

getTransformer

protected AttributeTransformer getTransformer()

Return the method.

getObject

protected Object getObject()

Return the receiver.

instantiate

protected T instantiate()
                 throws DescriptorException

Instantiate the object by executing the method on the transformer.

Specified by:

instantiate in class DatabaseValueHolder<T>

Throws:

DescriptorException

instantiate

protected T instantiate(Object object,
 AbstractSession session)
                 throws DescriptorException

Throws:

DescriptorException

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()

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 instantiated all fields can not be reset. Note: This method is not thread-safe. It must be used in a synchronized manner

Specified by:

isPessimisticLockingValueHolder in class DatabaseValueHolder<T>

setTransformer

protected void setTransformer(AttributeTransformer theTransformer)

Set the transformer.

setObject

protected void setObject(Object theObject)

Set the receiver.