JPA force DB query when entity is already saved in 1st cache

Solution

As you know, when we em.persist(entity), we keep the PK as the key and the entity itself as the value in EntityManger. We can think of EntityManager as PersistenceContext, although it is different in some minor ways.

Anyway, this entity is managed by EM and is saved in 1차 cache so that within the same database transaction, if another call is made to save or search or update this entity, EM can return it straight from its 1차 cache and not save a SQL query to be queried to DB once transaction.commit() is invoked.

But for logging purpose or to forcefully send the DB query, we have to get rid of this entity from being managed by EM.

Solution:

em.flush();
em.clear();

These 2 commands will do the trick. Remember flush does not flush out saved entities but it just sends out the query to DB immediately, even before transaction.commit() can happen.