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Hey,

Basically my problem is when you have multiple relationships in one entity, and the fetch type of all them is eager then I get the error relating to how hibernate cannot fetch multiple bags at once. But if I switch some to lazy I cannot get access to the collection and it says no session or session is closed. The question is how do I go about getting access to a lazily loaded collection if I must switch some from fetch type eager to lazy?

thanks in advance for your assistance


Hibernate version:
hibernate 3.2
Mapping documents:
RELATIONSHIP 1:(SWITCHING THIS ONE BETWEEN EAGER AND LAZY)
@OneToMany(fetch=FetchType.EAGER, cascade=CascadeType.ALL)

RELATIONSHIP 2:
@ManyToOne(fetch=FetchType.EAGER, targetEntity=pack.Region.class)
@JoinColumn(name="REGION_FK", referencedColumnName="Area", nullable=true)

RELATIONSHIP 3:
@OneToOne(fetch=FetchType.EAGER, cascade = CascadeType.ALL)
@PrimaryKeyJoinColumn

Code between sessionFactory.openSession() and session.close():

Full stack trace of any exception that occurs:
IF THERE ARE MULTIPLE RELATIONSHIPS WITH FETCH TYPE EAGER, THE ERROR IS:

Caused by: org.hibernate.HibernateException: cannot simultaneously fetch multiple bags

IF I CHANGE ONE OF THE RELATIONSHIPS TO FETCH TYPE LAZY AND TRY TO ACCESS THE COLLECTION I GET THE FOLLOWING ERROR;

org.hibernate.LazyInitializationException <init>
SEVERE: failed to lazily initialize a collection of role: pack.singles, no session or session was closed

Name and version of the database you are using:

The generated SQL (show_sql=true):

Debug level Hibernate log excerpt:


Problems with Session and transaction handling?

Read this: http://hibernate.org/42.html

The link here is basically my problem, the session is closed before the lazy loaded collections can be accessed. Are there any examples anywhere of how to load the lazy collections in the query before the session closes, because that seems to be where this is headed.

thanks in advance

http://www.hibernate.org/hib_docs/refer ... mance.html

Section 19.1.1

s = sessions.openSession();
Transaction tx = s.beginTransaction();

User u = (User) s.createQuery("from User u where u.name=:userName")
.setString("userName", userName).uniqueResult();
Map permissions = u.getPermissions();

tx.commit();
s.close();

Integer accessLevel = (Integer) permissions.get("accounts"); // Error!

Hey,

Here are some good resources for anybody who might run into a similar problem. Explains how to use fetch to load the lazy collections which resolves the problem.

http://gary.teaching.googlepages.com/Hi ... rial09.pdf
http://www.realsolve.co.uk/site/tech/or ... rmance.php

Thank you, these links helped me. I had the same problem. I switched my 'bag' implementations of collections to 'set'.