javax.persistence.LockModeType Maven / Gradle / Ivy
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package javax.persistence;
/**
* Lock modes that can be specified by means of the
* {@link EntityManager#lock EntityManager.lock()} method.
*
* The semantics of requesting locks of type
* {@link LockModeType#READ LockModeType.READ} and {@link
* LockModeType#WRITE LockModeType.WRITE} are the following.
*
*
If transaction T1 calls lock(entity, {@link
* LockModeType#READ LockModeType.READ}) on a versioned object,
* the entity manager must ensure that neither of the following
* phenomena can occur:
*
* - P1 (Dirty read): Transaction T1 modifies a row.
* Another transaction T2 then reads that row and obtains
* the modified value, before T1 has committed or rolled back.
* Transaction T2 eventually commits successfully; it does not
* matter whether T1 commits or rolls back and whether it does
* so before or after T2 commits.
*
-
*
P2 (Non-repeatable read): Transaction T1 reads a row.
* Another transaction T2 then modifies or deletes that row,
* before T1 has committed. Both transactions eventually commit
* successfully.
*
*
*
* Lock modes must always prevent the phenomena P1 and P2.
*
*
In addition, calling lock(entity, LockModeType.WRITE) on
* a versioned object, will also force an update (increment) to
* the entity's version column.
*
*
The persistence implementation is not required to support
* calling {@link EntityManager#lock EntityManager.lock()} on a
* non-versioned object. When it cannot support a such lock call,
* it must throw the {@link PersistenceException}.
*
*
* @since Java Persistence 1.0
*/
public enum LockModeType {
/** Read lock */
READ,
/** Write lock */
WRITE
}