Solve Hibernate Lazy-Init issue with hibernate.enable_lazy_load_no_trans

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The problem with this approach is that you can have the N+1 effect.

Imagine that you have the following entity:

public class Person{
    @OneToMany // default to lazy
    private List<Order> orderList;
}

If you have a report that returns 10K of persons, and if in this report you execute the code person.getOrderList() the JPA/Hibernate will execute 10K of queries. This is the N+1 effect, you will have no control about all the queries that will be executed.

Imagine now that Order is like below:

public class Order{
    @OneToMany // default to lazy
    private List<EmailSent> emailSentList;
}

Imagine now that you have a iteration with the person.getOrderList() and for every Order orderyou will do a order.getEmailSentList(). Can you see the problem now?

For LazyInitializationException you can have some solutions:

  • Use the OpenInSessionInView approach. You will need to create a WebFilter that will open and close the transaction. The problem with is the N+1 effect.
  • Use the hibernate.enable_lazy_load_no_trans configuration, that is a hibernate and you will not be able to port your project to other JPA provider if needed. You also can have the N+1 effect.
  • Use the EJB feature named PersistenceContext Extended. With this you will keep the context opened of several transactions. The problems are: N+1 effect can happen, use a lot of server memory (entities will stay managed)
  • Use the FETCH in the query. With this approach you could do a JPQL/HQL like: select p from Person p join fetch p.orderList. With this query you will have your list loaded from the database and will not have the N+1 effect. The problem is that you will need to write a JPQL for each case.

If you still have any problem, check these links:

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