Does having TransactionAttributeType.NOT_SUPPORTED on every DB lookup method makes sense? I don’t see the point in having the entity attached if it’s not going to execute an update.
@TransactionAttribute(TransactionAttributeType.NOT_SUPPORTED)
pubic List<AnEntity> getListEntities(){
TypedQuery<AnEntity> query = em.createNamedQuery("AnEntity.myQuery",AnEntity.class);
return query.getResultList();
}
Does it still end up in the cache?
The only time it seems useful to use the REQUIRED transcation propagation is when an update is required:
@TransactionAttribute(TransactionAttributeType.REQUIRED)
public void editPersonName(Integer id, String newName){
AnEntity anEntity= em.find(AnEntity.class, id);
anEntity.setName(newName);
}
Other than that I don’t really see the point.
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Answer
No, it doesn’t make sense to use the NOT_SUPPORTED transaction propagation for read-only queries, but it makes a lot of sense to use the default REQUIRED transaction propagation. You also need a transaction for reading data. The database always uses a transaction, no matter if you specify it or not.
Using an explicit transaction allows you to group several statements in a single transaction, and, if you are using Hibernate, you might avoid the aggressive connection release overhead.
Just because JPA allows you to execute read queries without a transaction, it doesn’t mean you have to do it this way.
The NOT_SUPPORTED mode is useful when you want to execute a service method outside of the current transaction scope. For example, when you have methods that don’t need a transaction at all (e.g sending an email) so that you avoid the overhead of starting/ending a transaction context.