JPA如何知道何时必须抛出OptimisticLockException? [英] How JPA knows when it have to throw OptimisticLockException?

问题描述

我想确认以下内容:

public void test() {

   SomeEntity se = em.find(SomeEntity.class, 1);

   // Do something...

   se.setField = "test";

}

JPA将仅对se执行乐观检查.

Here JPA will perform only optimistic check on se.

下一步:

public void test() {

   SomeEntity se = em.find(SomeEntity.class, 1);
   SomeOtherEntity soe = em.find(SomeOtherEntity.class, 1);
   em.lock(soe, LockModeType.OPTIMISTIC);

   // Do something...

   se.setField = "test";

}

如果自上次读取以来更改了se或soe(数据库中的版本增加)，则JPA将引发OptimisticException.

Here JPA will throw OptimisticException if se OR soe have been changed (version incremented in database) since last read.

是真的吗?

推荐答案

OptimisticLockException 仅在事务提交到您调用em.flush()的数据库时才抛出-然后，JPA Provider将比较版本字段和数字知道它被另一个转蛋白改变了.

OptimisticLockException will be throw only when transaction commits to database ore you call em.flush() - then JPA Provider will compare version field and figure out that it was changed by another transactoin.

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