org.eclipse.persistence.descriptors

Class ChangedFieldsLockingPolicy

java.lang.Object

org.eclipse.persistence.descriptors.FieldsLockingPolicy

org.eclipse.persistence.descriptors.ChangedFieldsLockingPolicy

All Implemented Interfaces:

java.io.Serializable, java.lang.Cloneable, org.eclipse.persistence.internal.descriptors.OptimisticLockingPolicy

public class ChangedFieldsLockingPolicy
extends FieldsLockingPolicy

Purpose: An implementation of the OptimisticLockingPolicy interface. This policy compares only the changed fields in the WHERE clause when doing an update. If any field has been changed, an optimistic locking exception will be thrown. A delete will only compare the primary key.

NOTE: This policy can only be used inside a unit of work.

Since:

TopLink 2.1

Author:

Peter Krogh

See Also:

Serialized Form

Nested Class Summary

Nested classes/interfaces inherited from interface org.eclipse.persistence.internal.descriptors.OptimisticLockingPolicy

org.eclipse.persistence.internal.descriptors.OptimisticLockingPolicy.LockOnChange

Constructor Summary

Constructors

Constructor and Description
ChangedFieldsLockingPolicy() PUBLIC: Create a new changed fields locking policy.

Method Summary

Methods

Modifier and Type	Method and Description
void	addLockValuesToTranslationRow(ObjectLevelModifyQuery query) INTERNAL: Values to be included in the locking mechanism are added to the translation row.
Expression	buildDeleteExpression(org.eclipse.persistence.internal.helper.DatabaseTable table, Expression mainExpression, org.eclipse.persistence.internal.sessions.AbstractRecord row) INTERNAL: When given an expression, this method will return a new expression with the optimistic locking values included.

Methods inherited from class org.eclipse.persistence.descriptors.FieldsLockingPolicy

addLockFieldsToUpdateRow, buildUpdateExpression, clone, compareWriteLockValues, getBaseValue, getLockOnChangeMode, getValueToPutInCache, getVersionDifference, getWriteLockField, getWriteLockUpdateExpression, getWriteLockValue, initialize, initializeProperties, isCascaded, isNewerVersion, isNewerVersion, isStoredInCache, mergeIntoParentCache, mergeIntoParentCache, setDescriptor, setLockOnChangeMode, setupWriteFieldsForInsert, shouldUpdateVersionOnMappingChange, shouldUpdateVersionOnOwnedMappingChange, supportsWriteLockValuesComparison, updateRowAndObjectForUpdate, validateDelete, validateUpdate

Methods inherited from class java.lang.Object

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

Constructor Detail

ChangedFieldsLockingPolicy

public ChangedFieldsLockingPolicy()

PUBLIC: Create a new changed fields locking policy. This locking policy is based on locking on all changed fields by comparing with their previous values to detect field-level collisions. Note: the unit of work must be used for all updates when using field locking. Without a unit of work, there is no way for to know what the original values were without the back up clone in the unit of work.

Method Detail

addLockValuesToTranslationRow

public void addLockValuesToTranslationRow(ObjectLevelModifyQuery query)

INTERNAL: Values to be included in the locking mechanism are added to the translation row. For changed fields the normal build row is ok as only changed fields matter.

Specified by:

addLockValuesToTranslationRow in interface org.eclipse.persistence.internal.descriptors.OptimisticLockingPolicy

Specified by:

addLockValuesToTranslationRow in class FieldsLockingPolicy

buildDeleteExpression

public Expression buildDeleteExpression(org.eclipse.persistence.internal.helper.DatabaseTable table,
                               Expression mainExpression,
                               org.eclipse.persistence.internal.sessions.AbstractRecord row)

INTERNAL: When given an expression, this method will return a new expression with the optimistic locking values included. The values are taken from the passed in database row. This expression will be used in a delete call. No new criteria will be added for changed fields.

Specified by:

buildDeleteExpression in interface org.eclipse.persistence.internal.descriptors.OptimisticLockingPolicy

Overrides:

buildDeleteExpression in class FieldsLockingPolicy