org.apache.openjpa.kernel
Interface LockManager

All Superinterfaces:

Closeable, LockLevels

All Known Subinterfaces:

JDBCLockManager

All Known Implementing Classes:

AbstractLockManager, NoneLockManager, PessimisticLockManager, VersionLockManager

public interface LockManager
extends Closeable, LockLevels

Handles obtaining and releasing locks on objects. The lock manager generally does not have to worry about synchronization, as the context is responsible for synchronizing the calls it makes to the lock manager.

Author:

Marc Prud'hommeaux

Field Summary

Fields inherited from interface org.apache.openjpa.kernel.LockLevels

LOCK_NONE, LOCK_READ, LOCK_WRITE

Method Summary

void	beginTransaction() Notification that a transaction is beginning.
void	close() Free any resources.
void	endTransaction() Notification that the current transaction has ended.
int	getLockLevel(OpenJPAStateManager sm) Return the lock level of the specified instance, or LockLevels.LOCK_NONE if not locked.
void	lock(OpenJPAStateManager sm, int level, int timeout, Object sdata) Obtain a lock on the specified object.
void	lockAll(Collection sms, int level, int timeout, Object sdata) Obtain locks on the specified objects.
void	release(OpenJPAStateManager sm) Release the lock on the given object.
void	setContext(StoreContext ctx) Set the context this lock manager is associated with.

Method Detail

setContext

void setContext(StoreContext ctx)

Set the context this lock manager is associated with. This will be invoked in the lock manager before any other methods are called.

getLockLevel

int getLockLevel(OpenJPAStateManager sm)

Return the lock level of the specified instance, or LockLevels.LOCK_NONE if not locked.

lock

void lock(OpenJPAStateManager sm,
          int level,
          int timeout,
          Object sdata)

Obtain a lock on the specified object. This method may be called when a user explicitly locks an object, and is also called automatically for every object accessed during a transaction. The implementation must track already-locked objects, and must be optimized to return quickly when the given object does not need additional locking. The lock manager might use the state manager's lock object for bookkeeping information.

Parameters:

sm - the object to lock

level - one of the lock constants defined in LockLevels, or a custom level

timeout - the timeout in milliseconds, or a negative number for no timeout

sdata - the context information passed from the store manager to the persistence context, if any; lock managers specific to a certain back end may be able to take advantage of this; others should ignore it

Throws:

LockException - if a lock cannot be obtained in the given number of milliseconds

See Also:

OpenJPAStateManager.setLock(java.lang.Object)

lockAll

void lockAll(Collection sms,
             int level,
             int timeout,
             Object sdata)

Obtain locks on the specified objects.

See Also:

lock(org.apache.openjpa.kernel.OpenJPAStateManager, int, int, java.lang.Object)

release

void release(OpenJPAStateManager sm)

Release the lock on the given object. This method will be called automatically for each state manager with a lock object set on transaction completion, just before the call to endTransaction(). The lock manager should null the state manager's lock object. Note that some state manager may be garbage collected during a transaction; thus lock managers cannot rely on this method being called for every state manager.

See Also:

OpenJPAStateManager.setLock(java.lang.Object)

beginTransaction

void beginTransaction()

Notification that a transaction is beginning. Locks are only obtained within transactions, so an implementation might use this method to initialize bookkeeping datastructures, etc.

endTransaction

void endTransaction()

Notification that the current transaction has ended. Clear all datastructures, release any left over locks, etc.

close

void close()

Free any resources.

Specified by:

close in interface Closeable