【文档摘要】J2EE Persistence - Controlling Concurrent Access to Entity Data with Locking

short term read lock / long term write lock

Optimistic Locking: version column

Pessimistic Locking: create a transaction to obtain long term lock

Lock Modes:

OPTIMISTIC: Obtain an optimistic read lock for all entities with version attributes.

OPTIMISTIC_FORCE_INCREMENT: Obtain an optimistic read lock for all entities with version attributes, andincrement the version attribute value.

READ:  OPTIMISTIC.

WRITE: OPTIMISTIC_FORCE_INCREMENT.

PESSIMISTIC_READ: immediately obtain a long-term read lock on the data toprevent the data being
modified or deleted. Other transactions may read the data while the lock is maintained, but not modify or delete the data.

PESSIMISTIC_WRITE: immediately obtain a long-term write lock on the data toprevent the data being
read, modified ordeleted.

PESSIMISTIC_FORCE_INCREMENT: immediately obtain a long-term lock on the data toprevent the data being
modified or deleted, and increment the version attribute value.

NONE: no additional locking.

Question:

How to choose which mode to use????

参考资料：
https://docs.oracle.com/javaee/7/tutorial/doc/persistence-locking001.htm#GKJHZ
https://blogs.oracle.com/carolmcdonald/entry/jpa_2_0_concurrency_and