How Can I create a Unit Test in Java that Can ensure that my JPA database entities are being loaded lazily?

Question

I would like to create unit tests for the persistence tier of my project to ensure that entities are being loaded lazily. I am using hibernate with springsource. What is a basic unit test that can guarantee that I can create an Assertion to check that? The challenge here for me at least is that while in the transaction I cannot tell if the entities are being fetched lazily and loaded upon demand or eagerly fetched.

Thanks

Answer 1

If you have a detached object, when you try to access the property, hibernate will throw a LazyInitializationException.

@Test(expected=LazyInitializationException.class)
public void lazyLoadTest() {
  //get a session object
  Session session = dao.getSession(); 

  //load object
  Foo foo = dao.findById(1);

  //if you have a detached object, this would be unnessary
  session.close();  

  //if lazy loading is working, an exception will be thrown
  //note: If you don't try to access the collection (.size(), the data will not be fetched)
  foo.getBars().size(); 
}

You can also use Hibernate.isInitialized

@Test
public void anotherLazyLoadTest() {
      //get a session object
      Session session = dao.getSession(); 

      //load object
      Foo foo = dao.findById(1);

      //if you have a detached object, this would be unnessary
      session.close();  

      boolean isInitialized = Hibernate.isInitialized(foo.getBars());
      assertFalse(isInitialized);
}