使用JPA表独占锁定 [英] Table exclusive lock with JPA

问题描述

是否可以以数据库无关的方式使用JPA专门锁定整个表（例如，不使用本机查询）？到目前为止，我只看到 EntityManager.lock（*） 但这只会锁定给定记录。

Is it possible to lock exclusively entire table with JPA in database agnostic way (without using native queries for instance)? So far I saw only EntityManager.lock(*) but this locks only given record.

推荐答案

我认为JPA本身并不支持这种情况 - 您总是锁定单个实体或每个查询结果的实体。始终允许插入，因为它们是新实体。您可以使用本机查询来使用数据库服务器支持的SQL来触发锁定，或者您需要以编程方式锁定插入。

I don't think this is supported by JPA natively - you always lock single entity or every entity which is a result from a query. Inserts are always allowed as they are new entities. You may either use native query to trigger a lock using SQL supported by your DB server, or you need to lock your insert programmatically.

通过编程方式，我的意思是你需要在每次插入之前获取一个锁。您可以通过创建一个单独的锁实体类，每个实体用于要锁定的表，然后在每次插入之前，使用如下的读锁锁定特定实体：

By programmatically I mean that you need to acquire a lock before every insert. You may do it by creating a separate lock entity class, each entity for a table you want to lock, and then before each insert, you lock particular entity with a read lock like this:

em.createQuery("select l from TableLock l where l.entity = :entityName", TableLock.class)
   .setParameter("entityName", MyEntity.class.getSimpleName())
   .setLockMode(LockModeType.PESSIMISTIC_READ)
   .getResultList();
em.persist(new MyEntity());

当然，您还应检查数据库中是否存在锁实体，如果不存在，则创建它首先，实体字段是您实体的名称。

Of course, you should also check if the lock entity exists in database, and if not, create it first, with entity field being the name of your entity.

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