How does lazy fetching work in Hibernate?

Question

I have configured my userDetails class with lazy fetching, and I have also configured my settings for lazy fetching. I am running this code:

 userDetails user = new userDetails();

    user.setUserName("Fenil");

     Address address = new Address();
     address.setCity("baroda");
     address.setState("gujarat");
     user.getListOfAddress().add(address);

    SessionFactory sessionfactory = new          
    Configuration().configure().buildSessionFactory();
    Session session = sessionfactory.openSession();
    session.beginTransaction();

    session.save(user);
    system.out.println(user.getName()); //sop1
    session.getTransaction().commit();
    session.close();
    system.out.println(user.getName());  //sop2

When I run the code above it gives me the value of username. But, if I replace sop line right after session.close() then it's throwing an exception.

My question is:

If I print the sop1 line before closing the session it should give me the username, and after closing the session the line marked sop2 should throw an exception, but instead it's returning the value of username. Why?

@BoristheSpider here is an answer http://stackoverflow.com/questions/2990799/difference-between-fetchtype-lazy-and-eager-in-java-persistence — Dipesh Raichana, Mar 17 '15 at 15:58
@gotchha that seems to be about `lazy` fetching... (don't worry, I was just being facetious). — Boris the Spider, Mar 17 '15 at 15:59

score 1 · Accepted Answer · answered Mar 17 '15 at 15:55

1

Lazy fetching still fetches only once, storing the result for subsequent calls. During your second call, the data has already been fetched, so it can be returned even after the session was closed.

answered Mar 17 '15 at 15:55

duckstep

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so is it like caching? – Dipesh Raichana Mar 17 '15 at 15:56
Kind of, if you think of your entities as the cache. – duckstep Mar 17 '15 at 15:57
is there any solution to prevent it? – Dipesh Raichana Mar 17 '15 at 15:59
Re-fetching the entity from a new transaction will start over the lazy fetching, but the values might still come from the Hibernate cache. Is there any reason why you would want to fetch that data on every access? If you're worried about stale data, use optimistic locking with a version column. – duckstep Mar 17 '15 at 16:12
thnx for your reply. I was just checking that session is closed properly or not. – Dipesh Raichana Mar 17 '15 at 17:22

How does lazy fetching work in Hibernate?

1 Answers1