Grails and Hibernate's Lazy Initialization Exception

Question

Where are the most common places where you've gotten an org.hibernate.LazyInitializationException in Grails, what was the cause and how did you solve it ?

I think this one exception comes up a lot for novice, so if you'd provide more examples, it would be great.

Answer 1

Lets take an example :

class Book {
  String title
  Author author
}

class Author {
  ...
}

Book book = Book.get(1)

As we know, default fetch mode is lazy in domain classes. Considering the above example, say we get the book object, then Book object gets attached to the hibernate session object i.e first level cache automatically. And after the domain object gets detached from the session object and then we try to fetch book.author, at this moment it raises the Lazy initialization exception.

So the solution is, to have either fetch mode as eager or attach your book object to hibernate session using the code given below :

if(!book.isAttached()){
     book.attach()
}

The description given above is one of the scenario. There could be many more. I request others to please share.