Question

I’m trying to update an entity using JPA with Google App Engine. I start a transaction, retrieve the entity to update, change a few fields, call persist and commit. Everything is executed without any error, however, the entity is not modified.

Here is the sample code:

EntityTransaction tx = entityManager.getTransaction();
try {
        tx.begin();
        DomainName domain = entityManager.find(DomainName.class, domainName);
        domain.setExists(body != null);
        domain.setHttpBody(body);
        domain.setHttpTimeStamp(new Date());
        entityManager.persist(domain);
        tx.commit();
} finally {
        if (tx.isActive()) {
                tx.rollback();
        }
}

What should I do to persist the entity using JPA?

Answer 1

No idea what the persist() call is doing, since the object (if found, which you don’t tell us) will be in managed state, hence the first update of a field marks the object as dirty, and will be committed on the commit() call. Obviously a simple inspection of the log would tell you what was happening.