Module org.eclipse.persistence.core
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
See Also:

  • Field Details

  • Constructor Details

    • FieldsLockingPolicy

      protected 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 Details

    • 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<DatabaseField> 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 <T> T 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 <T> T 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 <T> T 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<DatabaseField> 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