CODEWITHSUNDEEP
javajpa
danny
danny

Reputation: 3256

Will JPA EntityManager's merge method lead to OptimisticLockException?

Let's say I would like to merge a detached entity. when I do

T mergedEntity = entityManager.merge(detachedEntity);

the entityManager will load an entity (with same identifier with the detachedEntity) from database and copy all the data from the detachedEntity to the new loaded entity. When later my transaction ends, this entity will be saved to the database.

However, in a concurrent scenario, the entity in the database can be updated by other transactions between the entity is firstly loaded in my transaction and then flushed at the end of my transaction. In this case, I would like to know whether an OptimisticLockException will be thrown? If so, why the merge API doesn't specify the OptimisticLockException in Java doc? http://docs.oracle.com/javaee/6/api/javax/persistence/EntityManager.html#merge(T)

thanks

Upvotes: 2

Views: 3842

Answers (2)

Marcel Stör
Marcel Stör

Reputation: 23525

Will JPA EntityManager's merge method lead to OptimisticLockException?

No, not directly.

I would like to know whether an OptimisticLockException will be thrown? If so, why the merge API doesn't specify the OptimisticLockException in Java doc?

An OptimisticLockException can obviously only be thrown if you configured optimistic locking at all. Furthermore, since it inherits from java.lang.RuntimeException the merge method wouldn't have to declare it anyway.

BUT this is all hypothetical because OptimisticLockException isn't even thrown during the merge phase but while flushing changes to the datasource.

Upvotes: 3

JB Nizet
JB Nizet

Reputation: 691635

Because the merge() method is not what will throw this exception. This exception will be thrown when the state of the entity, in memory, will be flushed to the database. That doesn't happen when merge() is called, when flush() is called, either explicitely, or before the commit, or before a query is executed.

Upvotes: 4

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