主要是为了在OneFeed里测试一下<table>。
| Lock Mode | Description |
|---|---|
| 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, and increment the version attribute value. |
| PESSIMISTIC_READ | Immediately obtain a long-term read lock on the data to prevent the data from being modified or deleted. Other transactions may read the data while the lock is maintained, but may not modify or delete the data. The persistence provider is permitted to obtain a database write lock when a read lock was requested, but not vice versa. |
| PESSIMISTIC_WRITE | Immediately obtain a long-term write lock on the data to prevent the data from being read, modified, or deleted. |
| PESSIMISTIC_FORCE_INCREMENT | Immediately obtain a long-term lock on the data to prevent the data from being modified or deleted, and increment the version attribute of versioned entities. |
| READ | 来自JPA 1.0，OPTIMISTIC的同义词。 |
| WRITE | 来自JPA 1.0，OPTIMISTIC_FORCE_INCREMENT的同义词。 |
| NONE | 不加应用任何锁机制 |
可以通过多种途径设置锁，
EntityManager em = ...;
Person person = ...;
em.lock(person, LockModeType.OPTIMISTIC);
String personPK = ...;
Person person = em.find(Person.class, personPK,
LockModeType.PESSIMISTIC_WRITE);
String personPK = ...;
Person person = em.find(Person.class, personPK);
...
em.refresh(person, LockModeType.OPTIMISTIC_FORCE_INCREMENT);
Query q = em.createQuery(...);
q.setLockMode(LockModeType.PESSIMISTIC_FORCE_INCREMENT);
@NamedQuery(name="lockPersonQuery",
query="SELECT p FROM Person p WHERE p.name LIKE :name",
lockMode=PESSIMISTIC_READ)
其它参考