Does Hibernate 1st Cache work with HibernateTemplate?

0
votes

I am trying to dive a little deeper into Hibernate cache and Spring's HibernateTemplate, and I am kinda confused by the following questions:

1) How does HibernateTemplate manages the Hibernate session? If I invokes methods such as "getHibernateTemplate().find" and "getHibernateTemplate().execute()", will everytime HibernateTemplate opens a new Hibernate session to process?

2) Hibernate 1st cache works in the scope of Hibernate session. In this regards, if HibernateTemplate always open a new session to exeucte/find, then does it mean the Hibernate 1st cache is NOT usable with HibernateTemplate? (because the cached object will be destroyed anyway, and the next find() has to make a fresh query to get everything again from DB)

3) It seems Hibernate 1st cache holds a map of all objects fetched during the life of a session. In this case, if I query a object which had been fetched before in the same session, then I should get the object and all its data directly from the cache? In this regards, what happens if the data of this object has been modified in the database?

4) Hibernate 1st cache returns the data in format of objects, in this regards, if I use HQL to fetch only a few columns (attributes) from a table (object), will those data (objects with only part of its attributes being filled) also be cached?

Thanks a lot!

-------------------------- Additional Info --------------------------

Thanks to the hint from Alessio, I re-checked the Spring specification and the following is my understanding:

If I call the getHibernateTemplate() within a existing transaction block (e.g., behind "session.beginTransaction();"), then HibernateTemplate will use the existing transaction to execute.

If I call getHibernateTemplate() with no transaction in current thread, then getHibernateTemplate() will actually call "openSession()" instead of "getCurrentSession()" because there is NO transaction (even when openSession() had been called before and an opened session was already bound to current thread), and a new session will be created and given to getHibernateTemplate(). Once the getHibernateTemplate has done its work, the newly created session will be destroyed.

Am my understanding right?

1
springhibernatehql

1 Answers

2
votes

The Spring documentation says the following about session access and creation:

"HibernateTemplate is aware of a corresponding Session bound to the current thread, for example when using HibernateTransactionManager. If allowCreate is true, a new non-transactional Session will be created if none is found, which needs to be closed at the end of the operation. If false, an IllegalStateException will get thrown in this case."

So, whether it creates a new session or not depends on the allowCreate property and the presence of an interceptor that sets up a session for the current thread. Note also that HibernateTemplate is capable of falling back to Hibernate's SessionFactory.getCurrentSession().

-------------------------- Additional Info --------------------------

Edit: to answer to the additional question by the author, the documentation is not very explicit about this, but a session is obtained or created when getSession() is called, which includes calls to execute() of course. A session is not created or accessed in any way when you only instantiate a HibernateTemplate or get it from an application context, as the call to getHibernateTemplate() presumably does.