Lists not returning expected content

torpid · **Joined:** Fri Oct 21, 2005 4:49 am **Posts:** 13

Hibernate version:
3.0.5
Name and version of the database you are using:
MySQL 4.1.14

At the beginning and end of each JSP page in my application, I open and close the Hibernate session using the HibernateUtil class from the book with ThreadLocals.

Everything works except lists on the join table of a many to many relationship. I have another m-n join table which does work, but the broken one, AonB, alos contains extraInformation. The mapping files are set up so that As have a many to many to Bs and vice versa AND both As and Bs each have a one to many relation to As on Bs.

When fetching a list using

Code:

createQuery("from AonB").list();// OR
createQuery("from AonB where aid=:aid").setString("aid", getAID()).list();

a list of the correct size (I can check the DB with mySQL Query Browser, so I know DB is correct) is returned but the list contains duplicates and hence not all the correct lines....?!

Any help greatly appreciated

kochcp · **Posted:** Wed Nov 09, 2005 12:28 pm

correct me if I'm wrong, but isn't a join on a many to many relatoinship going to return lots of repeat data?

If this is being returned as a List of Arrays of Objects (one array of object for each satisfied join condition containing one object A and one object B), you will get many copies of A per each B it matches up with.

torpid · **Joined:** Fri Oct 21, 2005 4:49 am **Posts:** 13

When I say join table, I may have used incorrect terminology.
It's just a table with 3 columns, 2 foreign keys and the extra information to relate 2 other tables.

"from AonB" should return all the rows in the table and it does return a list of the right size...

pmularien · **Posted:** Wed Nov 09, 2005 1:27 pm

Mapping file(s)?

torpid · **Joined:** Fri Oct 21, 2005 4:49 am **Posts:** 13

The mapping files can be seen here:
http://forum.hibernate.org/viewtopic.php?p=2267520#2267520

Maybe I should point out that I do have a class AonB to represent the items in the AonB table. I'm also using java5 and forcing the output from the list() method into a List<AonB> which raises an unchecked warning from the compiler.

Same problem with Hibernate 3.1 rc2 too.

Thanks for your help

torpid · **Joined:** Fri Oct 21, 2005 4:49 am **Posts:** 13

Using the createSQLQuery(...) method has no effect either.

I assume that it can't be a bug in Hibernate becuase it would be really serious and someone would've fixed it already.
Could it be something to do with lazy loading? But I don't have this problem doing the exact same code on other tables...

Therefore I suspect the rather dodgy mapping file for AonB which middlegen generated. However, this file does work in all other cases whereas any 'correct' manually edited versions of the file do not initialise.

torpid · **Joined:** Fri Oct 21, 2005 4:49 am **Posts:** 13

Aha! It's not random, it's becuase it's using the extraInfo as the key instead of the 2 FKs.

This is due to the middlegen generated mapping file (see link above). I have tried to fix this in the past, but to no avail. Any ideas?