void lock(
  Object entity, 
  LockModeType lockMode, 
  LockOption... options
)

Lock an entity instance belonging to the persistence context, obtaining the specified plain, using the specified plain.

If a pessimistic lock mode type is specified and the entity contains a version attribute, the persistence provider must also perform optimistic version checks when obtaining the database lock. If these checks fail, the OptimisticLockException is thrown.

If the lock mode type is pessimistic and the entity instance is found but cannot be locked:

• the PessimisticLockException is thrown if the database locking failure causes transaction-level rollback
• the LockTimeoutException is thrown if the database locking failure causes only statement-level rollback

If a vendor-specific LockOption is not recognized, it is silently ignored.

Portable applications should not rely on the standard plain. Depending on the database in use and the locking mechanisms used by the provider, the option may or may not be observed.