Module org.datanucleus

Package org.datanucleus.state

Interface LockManager

All Known Implementing Classes:

LockManagerImpl

public interface LockManager

Interface defining a manager for locking of objects. There are currently two modes to a LockManager.

1. Where the user has the object and wants it locking. In this case they provide StateManager and we lock it (by a call to the datastore where appropriate).
2. Where the user wants to do a find of an object with a particular id. In this case we register the identity as needing this lock level, and the datastore will be called to retrieve the object and will check back what lock level to use.

The LockManager controls all aspects of what objects need any form of locking, the updates to versions, and version checking (optimistic locking).

Method Summary

Modifier and Type	Method	Description
void	clear()	Method to clear all settings of required lock level.
void	close()	Method to close the manager and release resources.
LockMode	getLockMode(Object id)	Accessor for what locking should be applied to the object with the specified identity (mode 2).
LockMode	getLockMode(DNStateManager sm)	Accessor for the current lock mode for the object managed by the passed StateManager (mode 1).
Object	getNextVersion(VersionMetaData vermd, Object currentVersion)	Convenience method to provide the next version to use given the VersionMetaData and the current version.
void	lock(Object id, LockMode lockMode)	Method to lock the object with the provided identity (mode 2).
void	lock(DNStateManager sm, LockMode lockMode)	Method to lock the object managed by the passed StateManager (mode 1).
void	performOptimisticVersionCheck(DNStateManager sm, VersionStrategy versionStrategy, Object versionDatastore)	Method to perform an optimistic version check on the specified StateManager.
void	unlock(DNStateManager sm)	Method to unlock the object managed by the passed StateManager (mode 1).

Method Detail

lock

void lock(DNStateManager sm,
          LockMode lockMode)

Method to lock the object managed by the passed StateManager (mode 1).

Parameters:

sm - StateManager for the object

lockMode - mode for locking

unlock

void unlock(DNStateManager sm)

Method to unlock the object managed by the passed StateManager (mode 1).

Parameters:

sm - StateManager for the object

getLockMode

LockMode getLockMode(DNStateManager sm)

Accessor for the current lock mode for the object managed by the passed StateManager (mode 1).

Parameters:

sm - StateManager for the object

Returns:

The lock mode

lock

void lock(Object id,
          LockMode lockMode)

Method to lock the object with the provided identity (mode 2).

Parameters:

id - Identity of the object

lockMode - mode for locking

getLockMode

LockMode getLockMode(Object id)

Accessor for what locking should be applied to the object with the specified identity (mode 2).

Parameters:

id - The identity

Returns:

The lock mode to apply (NONE if nothing defined)

clear

void clear()

Method to clear all settings of required lock level.

close

void close()

Method to close the manager and release resources.

performOptimisticVersionCheck

void performOptimisticVersionCheck(DNStateManager sm,
                                   VersionStrategy versionStrategy,
                                   Object versionDatastore)

Method to perform an optimistic version check on the specified StateManager.

Parameters:

sm - StateManager

versionStrategy - The version strategy in use

versionDatastore - Version of the object in the datastore

getNextVersion

Object getNextVersion(VersionMetaData vermd,
                      Object currentVersion)

Convenience method to provide the next version to use given the VersionMetaData and the current version.

Parameters:

vermd - Version metadata

currentVersion - The current version

Returns:

The next version

Throws:

NucleusUserException - Thrown if the strategy is not supported.