Module org.eclipse.persistence.core
Package org.eclipse.persistence.internal.indirection

Class UnitOfWorkValueHolder<T>

java.lang.Object
org.eclipse.persistence.internal.indirection.DatabaseValueHolder<T>
org.eclipse.persistence.internal.indirection.UnitOfWorkValueHolder<T>
All Implemented Interfaces:
Serializable, Cloneable, ValueHolderInterface<T>, WeavedAttributeValueHolderInterface<T>, WrappingValueHolder<T>
Direct Known Subclasses:
UnitOfWorkQueryValueHolder, UnitOfWorkTransformerValueHolder
public abstract class UnitOfWorkValueHolder<T> extends DatabaseValueHolder<T> implements WrappingValueHolder<T>
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.
See Also:

  • Field Details

    • wrappedValueHolder

      protected transient ValueHolderInterface<T> wrappedValueHolder
      The value holder in the original object.

    • mapping

      protected transient DatabaseMapping mapping
      The mapping for the attribute.

    • backupValueHolder

      protected ValueHolderInterface<T> backupValueHolder
      The value holder stored in the backup copy, should not be transient.

    • remoteUnitOfWork

      protected UnitOfWorkImpl remoteUnitOfWork
      These cannot be transient because they are required for a remote unit of work. When the remote uow is serialized to the server to be committed, these are used to reconstruct the value holder on the server. They should be null for non-remote sessions.

    • sourceObject

      protected Object sourceObject

    • relationshipSourceObject

      protected transient Object relationshipSourceObject
      This attribute is used specifically for relationship support. It mimics the sourceObject attribute which is used for RemoteValueholder

    • sourceAttributeName

      protected String sourceAttributeName

    • wrappedValueHolderRemoteID

      protected ObjID wrappedValueHolderRemoteID

  • Constructor Details

  • Method Details

    • buildBackupCloneFor

      protected abstract Object buildBackupCloneFor(Object cloneAttributeValue)
      Backup the clone attribute value.

    • buildCloneFor

      public abstract T buildCloneFor(Object originalAttributeValue)
      Clone the original attribute value.

    • getBackupValueHolder

      protected ValueHolderInterface<T> getBackupValueHolder()

    • getMapping

      public DatabaseMapping getMapping()

    • getRemoteUnitOfWork

      protected UnitOfWorkImpl getRemoteUnitOfWork()

    • getSourceAttributeName

      protected String getSourceAttributeName()

    • getSourceObject

      protected Object getSourceObject()

    • getRelationshipSourceObject

      protected Object getRelationshipSourceObject()

    • getUnitOfWork

      protected UnitOfWorkImpl getUnitOfWork()

    • getValueFromServerObject

      protected T getValueFromServerObject()
      This is used for a remote unit of work. If the value holder is sent back to the server uninstantiated and it needs to be instantiated, then we must find the original object and get the appropriate attribute from it.

    • instantiateImpl

      protected T instantiateImpl()
      a.k.a getValueFromWrappedValueholder. The old name is no longer correct, as query based valueholders are now sometimes triggered directly without triggering the underlying valueholder.

    • isEasilyInstantiated

      public boolean isEasilyInstantiated()
      INTERNAL: Answers if this valueholder is easy to instantiate.
      Overrides:
      isEasilyInstantiated in class DatabaseValueHolder<T>
      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<T>

    • getWrappedValueHolder

      public ValueHolderInterface<T> getWrappedValueHolder()
      Description copied from interface: WrappingValueHolder
      Returns the valueholder that is wrapped by this ValueHolder
      Specified by:
      getWrappedValueHolder in interface WrappingValueHolder<T>
      Overrides:
      getWrappedValueHolder in class DatabaseValueHolder<T>

    • getWrappedValueHolderRemoteID

      public 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<T>

    • instantiate

      protected T instantiate()
      Get the value from the wrapped value holder, instantiating it if necessary, and clone it.
      Specified by:
      instantiate in class DatabaseValueHolder<T>

    • 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.

      Specified by:
      instantiateForUnitOfWorkValueHolder in class DatabaseValueHolder<T>

    • 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<T>

    • resetFields

      protected void resetFields()
      Reset all the fields that are not needed after instantiation.
      Overrides:
      resetFields in class DatabaseValueHolder<T>

    • setBackupValueHolder

      public void setBackupValueHolder(ValueHolderInterface<T> backupValueHolder)

    • setMapping

      protected void setMapping(DatabaseMapping mapping)

    • setRemoteUnitOfWork

      protected void setRemoteUnitOfWork(UnitOfWorkImpl remoteUnitOfWork)

    • setSourceAttributeName

      protected void setSourceAttributeName(String name)

    • setSourceObject

      protected void setSourceObject(Object sourceObject)

    • setRelationshipSourceObject

      protected void setRelationshipSourceObject(Object relationshipSourceObject)

    • setWrappedValueHolder

      protected void setWrappedValueHolder(DatabaseValueHolder<T> valueHolder)

    • 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>