Package org.eclipse.persistence.descriptors

Class FieldsLockingPolicy

java.lang.Object

org.eclipse.persistence.descriptors.FieldsLockingPolicy

All Implemented Interfaces:

Serializable, Cloneable, OptimisticLockingPolicy

Direct Known Subclasses:

AllFieldsLockingPolicy, ChangedFieldsLockingPolicy, SelectedFieldsLockingPolicy

public abstract class FieldsLockingPolicy
extends Object
implements OptimisticLockingPolicy

Purpose: An abstract superclass of some implementations of the OptimisticLockingPolicy interface. All of the subclasses of this class implement OptimisticLocking based on mapped fields in the object. These fields are only compared and not modified. Any modification (incrementing etc..) must be handled by the application.

Since:

TopLink 2.1

Author:

Peter Krogh

See Also:

AllFieldsLockingPolicy, ChangedFieldsLockingPolicy, SelectedFieldsLockingPolicy, Serialized Form

Nested Class Summary

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

OptimisticLockingPolicy.LockOnChange

Field Summary

Fields

Modifier and Type	Field	Description
protected List<DatabaseField>	allNonPrimaryKeyFields
protected ClassDescriptor	descriptor

Constructor Summary

Constructors

Constructor	Description
FieldsLockingPolicy()	PUBLIC: Create a new field locking policy.

Method Summary

Modifier and Type	Method	Description
void	addLockFieldsToUpdateRow(AbstractRecord Record, AbstractSession session)	INTERNAL: Add update fields for template row.
abstract void	addLockValuesToTranslationRow(ObjectLevelModifyQuery query)	INTERNAL: Values to be included in the locking mechanism are added to the translation row.
protected List	buildAllNonPrimaryKeyFields()	INTERNAL: Returns the fields that should be compared in the where clause.
Expression	buildDeleteExpression(DatabaseTable table, Expression mainExpression, AbstractRecord row)	INTERNAL: When given an expression, this method will return a new expression with the optimistic locking values included.
protected Expression	buildExpression(DatabaseTable table, AbstractRecord transRow, AbstractRecord modifyRow, ExpressionBuilder builder)	INTERNAL: returns the expression to be used in both the delete and update where clause.
Expression	buildUpdateExpression(DatabaseTable table, Expression mainExpression, AbstractRecord transRow, AbstractRecord modifyRow)	INTERNAL: This method must be included in any locking policy.
Object	clone()	INTERNAL: Clone the policy
int	compareWriteLockValues(Object value1, Object value2)	INTERNAL: This method shouldn't be called if supportsWriteLockValuesComparison() returns false.
protected List<DatabaseField>	getAllNonPrimaryKeyFields()	INTERNAL: Returns the fields that should be compared in the where clause.
protected List<DatabaseField>	getAllNonPrimaryKeyFields(DatabaseTable table)	INTERNAL: filter the fields based on the passed in table.
Object	getBaseValue()	INTERNAL: This is the base value that is older than all other values, it is used in the place of null in some situations.
protected abstract List<DatabaseField>	getFieldsToCompare(DatabaseTable table, AbstractRecord transRow, AbstractRecord modifyRow)	INTERNAL: Returns the fields that should be compared in the where clause.
OptimisticLockingPolicy.LockOnChange	getLockOnChangeMode()	ADVANCED: returns the LockOnChange mode for this policy.
Object	getValueToPutInCache(AbstractRecord row, AbstractSession session)	INTERNAL: Return the value that should be stored in the identity map.
int	getVersionDifference(Object currentValue, Object domainObject, Object primaryKeys, AbstractSession session)	INTERNAL: Return the number of version difference between the two states of the object.
DatabaseField	getWriteLockField()	INTERNAL: Return the write lock field.
Expression	getWriteLockUpdateExpression(ExpressionBuilder builder, AbstractSession session)	INTERNAL:
Object	getWriteLockValue(Object domainObject, Object primaryKey, AbstractSession session)	INTERNAL: This method will return the optimistic lock value for the object
void	initialize(AbstractSession session)	INTERNAL: It is responsible for initializing the policy;
void	initializeProperties()	INTERNAL: It is responsible for initializing the policy;
boolean	isCascaded()	PUBLIC: Return true if the policy uses cascade locking.
boolean	isNewerVersion(Object currentValue, Object domainObject, Object primaryKey, AbstractSession session)	INTERNAL: Compares the value and the value from the object (or cache).
boolean	isNewerVersion(AbstractRecord Record, Object domainObject, Object primaryKey, AbstractSession session)	INTERNAL: Compares the value from the row and from the object (or cache).
protected boolean	isPrimaryKey(DatabaseField dbField)	INTERNAL: Returns whether or not this field is a primary key.
boolean	isStoredInCache()	PUBLIC: Return true if the lock value is stored in the cache.
void	mergeIntoParentCache(CacheKey unitOfWorkCacheKey, CacheKey parentSessionCacheKey)	INTERNAL: This method should merge changes from the parent into the child.
void	mergeIntoParentCache(UnitOfWorkImpl uow, Object primaryKey, Object object)	INTERNAL: Only applicable when the value is stored in the cache.
protected void	setAllNonPrimaryKeyFields(List allNonPrimaryKeyFields)	INTERNAL: Set method for all the primary keys
void	setDescriptor(ClassDescriptor descriptor)	INTERNAL: Set method for the descriptor
void	setLockOnChangeMode(OptimisticLockingPolicy.LockOnChange lockOnChangeMode)	ADVANCED: Sets the LockOnChange mode for this policy.
void	setupWriteFieldsForInsert(ObjectLevelModifyQuery query)	INTERNAL: Put the initial writelock value into the modifyRow.
boolean	shouldUpdateVersionOnMappingChange()	INTERNAL: Returns true if the policy has been set to set an optimistic read lock when any mapping changes.
boolean	shouldUpdateVersionOnOwnedMappingChange()	INTERNAL: Returns true if the policy has been set to set an optimistic read lock when a owning mapping changes.
boolean	supportsWriteLockValuesComparison()	INTERNAL: Indicates whether compareWriteLockValues method is supported by the policy.
void	updateRowAndObjectForUpdate(ObjectLevelModifyQuery query, Object domainObject)	INTERNAL: Nothing to do because all updates are handled by the application
void	validateDelete(int rowCount, Object object, DeleteObjectQuery query)	INTERNAL: Check the row count for lock failure.
void	validateUpdate(int rowCount, Object object, WriteObjectQuery query)	INTERNAL: Check the row count for lock failure.
protected void	verifyUsage(AbstractSession session)	INTERNAL: throw an exception if not inside a unit of work at this point

Methods inherited from class java.lang.Object

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

Field Detail

descriptor

protected ClassDescriptor descriptor

allNonPrimaryKeyFields

protected List<DatabaseField> allNonPrimaryKeyFields

Constructor Detail

FieldsLockingPolicy

public FieldsLockingPolicy()

PUBLIC: Create a new field locking policy. A field locking policy is based on locking on a subset of 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.

Method Detail

addLockFieldsToUpdateRow

public void addLockFieldsToUpdateRow(AbstractRecord Record,
                                     AbstractSession session)

INTERNAL: Add update fields for template row. These are any unmapped fields required to write in an update. Since all fields are mapped, there is nothing required.

Specified by:

addLockFieldsToUpdateRow in interface OptimisticLockingPolicy

addLockValuesToTranslationRow

public abstract void addLockValuesToTranslationRow(ObjectLevelModifyQuery query)

INTERNAL: Values to be included in the locking mechanism are added to the translation row. Set the translation row to all the original field values.

Specified by:

addLockValuesToTranslationRow in interface OptimisticLockingPolicy

buildAllNonPrimaryKeyFields

protected List buildAllNonPrimaryKeyFields()

INTERNAL: Returns the fields that should be compared in the where clause. In this case, it is all the fields, except for the primary key and class indicator fields. This is called during lazy initialization.

buildDeleteExpression

public Expression buildDeleteExpression(DatabaseTable table,
                                        Expression mainExpression,
                                        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.

Specified by:

buildDeleteExpression in interface OptimisticLockingPolicy

buildExpression

protected Expression buildExpression(DatabaseTable table,
                                     AbstractRecord transRow,
                                     AbstractRecord modifyRow,
                                     ExpressionBuilder builder)

INTERNAL: returns the expression to be used in both the delete and update where clause.

buildUpdateExpression

public Expression buildUpdateExpression(DatabaseTable table,
                                        Expression mainExpression,
                                        AbstractRecord transRow,
                                        AbstractRecord modifyRow)

INTERNAL: This method must be included in any locking policy. 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.

Specified by:

buildUpdateExpression in interface OptimisticLockingPolicy

clone

public Object clone()

INTERNAL: Clone the policy

Specified by:

clone in interface OptimisticLockingPolicy

Overrides:

clone in class Object

supportsWriteLockValuesComparison

public boolean supportsWriteLockValuesComparison()

INTERNAL: Indicates whether compareWriteLockValues method is supported by the policy. Numeric or timestamp lock values could be compared: for every pair of values v1 and v2 - either v1<v2; or v1==v2; or v1>v2. However it's impossible to compare values for FieldsLockingPolicy for two reasons: 1. there is no "linear order": v1<v2 and v>v2 is not defined: either v1==v2 or v1!=v2; 2. locking value is not a single field which is not part of mapped object value but rather a set of object's mapped fields. That means any object's mapped attribute change is potentially a change of the locking value. For ChangedFieldsLockingPolicy every mapped attribute's change is a change of locking value. The pattern used by versioning: "if the original locking value is unchanged then the object hasn't been changed outside of the application", which allows to distinguish between the change made inside and outside the application, doesn't work for fields locking. It degenerates into useless pattern: "if the original locking value is unchanged then the object hasn't been changed". Use compareWriteLockValues method only if this method returns true.

Specified by:

supportsWriteLockValuesComparison in interface OptimisticLockingPolicy

compareWriteLockValues

public int compareWriteLockValues(Object value1,
                                  Object value2)

INTERNAL: This method shouldn't be called if supportsWriteLockValuesComparison() returns false. This method compares two writeLockValues. The writeLockValues should be non-null and of the correct type. Returns: -1 if value1 is less (older) than value2; 0 if value1 equals value2; 1 if value1 is greater (newer) than value2. Throws: NullPointerException if the passed value is null; ClassCastException if the passed value is of a wrong type.

Specified by:

compareWriteLockValues in interface OptimisticLockingPolicy

getAllNonPrimaryKeyFields

protected List<DatabaseField> getAllNonPrimaryKeyFields()

INTERNAL: Returns the fields that should be compared in the where clause. In this case, it is all the fields, except for the primary key and class indicator field.

getAllNonPrimaryKeyFields

protected List<DatabaseField> getAllNonPrimaryKeyFields(DatabaseTable table)

INTERNAL: filter the fields based on the passed in table. Only return fields of this table.

getBaseValue

public Object getBaseValue()

INTERNAL: This is the base value that is older than all other values, it is used in the place of null in some situations.

Specified by:

getBaseValue in interface OptimisticLockingPolicy

getFieldsToCompare

protected abstract List<DatabaseField> getFieldsToCompare(DatabaseTable table,
                                                          AbstractRecord transRow,
                                                          AbstractRecord modifyRow)

INTERNAL: Returns the fields that should be compared in the where clause. This method must be implemented by the subclass

getWriteLockField

public DatabaseField getWriteLockField()

INTERNAL: Return the write lock field.

Specified by:

getWriteLockField in interface OptimisticLockingPolicy

getWriteLockUpdateExpression

public Expression getWriteLockUpdateExpression(ExpressionBuilder builder,
                                               AbstractSession session)

INTERNAL:

Specified by:

getWriteLockUpdateExpression in interface OptimisticLockingPolicy

getLockOnChangeMode

public OptimisticLockingPolicy.LockOnChange getLockOnChangeMode()

ADVANCED: returns the LockOnChange mode for this policy. This mode specifies if a Optimistic Write lock should be enforced on this entity when a set of mappings are changed. Unfortunately this locking policy can not enforce an optimistic write lock unless a FK or DTF field has changed so this type returns LockOnChange.NONE

Specified by:

getLockOnChangeMode in interface OptimisticLockingPolicy

getValueToPutInCache

public Object getValueToPutInCache(AbstractRecord row,
                                   AbstractSession session)

INTERNAL: Return the value that should be stored in the identity map. If the value is stored in the object, then return a null.

Specified by:

getValueToPutInCache in interface OptimisticLockingPolicy

getVersionDifference

public int getVersionDifference(Object currentValue,
                                Object domainObject,
                                Object primaryKeys,
                                AbstractSession session)

INTERNAL: Return the number of version difference between the two states of the object.

Specified by:

getVersionDifference in interface OptimisticLockingPolicy

getWriteLockValue

public Object getWriteLockValue(Object domainObject,
                                Object primaryKey,
                                AbstractSession session)

INTERNAL: This method will return the optimistic lock value for the object

Specified by:

getWriteLockValue in interface OptimisticLockingPolicy

initialize

public void initialize(AbstractSession session)

INTERNAL: It is responsible for initializing the policy;

Specified by:

initialize in interface OptimisticLockingPolicy

initializeProperties

public void initializeProperties()

INTERNAL: It is responsible for initializing the policy;

Specified by:

initializeProperties in interface OptimisticLockingPolicy

isStoredInCache

public boolean isStoredInCache()

PUBLIC: Return true if the lock value is stored in the cache.

Specified by:

isStoredInCache in interface OptimisticLockingPolicy

isCascaded

public boolean isCascaded()

PUBLIC: Return true if the policy uses cascade locking. Currently, not supported on this policy at this time.

Specified by:

isCascaded in interface OptimisticLockingPolicy

isNewerVersion

public boolean isNewerVersion(Object currentValue,
                              Object domainObject,
                              Object primaryKey,
                              AbstractSession session)

INTERNAL: Compares the value and the value from the object (or cache). Will return true if the object is newer than the row.

Specified by:

isNewerVersion in interface OptimisticLockingPolicy

isNewerVersion

public boolean isNewerVersion(AbstractRecord Record,
                              Object domainObject,
                              Object primaryKey,
                              AbstractSession session)

INTERNAL: Compares the value from the row and from the object (or cache). Will return true if the object is newer than the row.

Specified by:

isNewerVersion in interface OptimisticLockingPolicy

isPrimaryKey

protected boolean isPrimaryKey(DatabaseField dbField)

INTERNAL: Returns whether or not this field is a primary key. This method will also return true for secondary table primarykeys

mergeIntoParentCache

public void mergeIntoParentCache(UnitOfWorkImpl uow,
                                 Object primaryKey,
                                 Object object)

INTERNAL: Only applicable when the value is stored in the cache.

Specified by:

mergeIntoParentCache in interface OptimisticLockingPolicy

mergeIntoParentCache

public void mergeIntoParentCache(CacheKey unitOfWorkCacheKey,
                                 CacheKey parentSessionCacheKey)

INTERNAL: This method should merge changes from the parent into the child. #see this method in VersionLockingPolicy

Specified by:

mergeIntoParentCache in interface OptimisticLockingPolicy

setAllNonPrimaryKeyFields

protected void setAllNonPrimaryKeyFields(List allNonPrimaryKeyFields)

INTERNAL: Set method for all the primary keys

setDescriptor

public void setDescriptor(ClassDescriptor descriptor)

INTERNAL: Set method for the descriptor

Specified by:

setDescriptor in interface OptimisticLockingPolicy

setLockOnChangeMode

public void setLockOnChangeMode(OptimisticLockingPolicy.LockOnChange lockOnChangeMode)

ADVANCED: Sets the LockOnChange mode for this policy. This mode specifies if a Optimistic Write lock should be enforced on this entity when set of mappings are changed. Unfortunately this locking policy can not always force an optimistic lock unless the core fields have changed

Specified by:

setLockOnChangeMode in interface OptimisticLockingPolicy

setupWriteFieldsForInsert

public void setupWriteFieldsForInsert(ObjectLevelModifyQuery query)

INTERNAL: Put the initial writelock value into the modifyRow. There is nothing to do because all the lock values are in the mappings.

Specified by:

setupWriteFieldsForInsert in interface OptimisticLockingPolicy

updateRowAndObjectForUpdate

public void updateRowAndObjectForUpdate(ObjectLevelModifyQuery query,
                                        Object domainObject)

INTERNAL: Nothing to do because all updates are handled by the application

Specified by:

updateRowAndObjectForUpdate in interface OptimisticLockingPolicy

shouldUpdateVersionOnOwnedMappingChange

public boolean shouldUpdateVersionOnOwnedMappingChange()

INTERNAL: Returns true if the policy has been set to set an optimistic read lock when a owning mapping changes. Unfortunately this locking policy can not always force an optimistic lock unless the core fields have changed

Specified by:

shouldUpdateVersionOnOwnedMappingChange in interface OptimisticLockingPolicy

shouldUpdateVersionOnMappingChange

public boolean shouldUpdateVersionOnMappingChange()

INTERNAL: Returns true if the policy has been set to set an optimistic read lock when any mapping changes. Unfortunately this locking policy can not always force an optimistic lock unless the core fields have changed

Specified by:

shouldUpdateVersionOnMappingChange in interface OptimisticLockingPolicy

validateDelete

public void validateDelete(int rowCount,
                           Object object,
                           DeleteObjectQuery query)

INTERNAL: Check the row count for lock failure.

Specified by:

validateDelete in interface OptimisticLockingPolicy

validateUpdate

public void validateUpdate(int rowCount,
                           Object object,
                           WriteObjectQuery query)

INTERNAL: Check the row count for lock failure.

Specified by:

validateUpdate in interface OptimisticLockingPolicy

verifyUsage

protected void verifyUsage(AbstractSession session)

INTERNAL: throw an exception if not inside a unit of work at this point