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Hibernate - Using Join table - one-to-many association - Lazy Exception  RSS feed

Gilbert johnson
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Posts: 45
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First of all - want to thank everyone who contributes in this forum. It has helped me immensely so many times when I have been stuck.

Right now I am on my quest to learn hibernate and have already asked questions here before.

I have two tables - Group and Product which have a bi-directional many-to-many relationship. A group can have many products and a product can belong to many groups.

So I introduced a join table "Group_Product" - now this table has an extra column userID. So one of the members of this forum suggested two approaches - and I went with the approach of using two one-to-many associations. Everything is working fine.

Now I want to retrieve all products that belong to a particular Group.
In my Java Code - using groupId, I'm loading the Group object.
From my Group object - I'm getting a set of GroupProduct.
Now GroupProduct has objects Group and Product and userId as members.

Now in my java code, I have:

The code is printing userID and productID but throws an exception while printing productName.

I know thats because, its only querying Group and Group_Product table. Its not linking Group_Product table with Product table.

What am I missing. Really appreciate your responses.

Here are my hbm.xml files



[ March 26, 2008: Message edited by: Gilbert johnson ]
Mark Spritzler
Posts: 17309
IntelliJ IDE Mac Spring
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LazyInitializationExceptions occur when Hibernate tries to get data from the database, but there is no longer a Session open. Basically, where you are trying to access the other data Hibernate wants to run a query against the database, but it can't get a Connection to the database, which it gets from the Session object, which is no longer open or available.

It is sorta covered in the JavaRanch Style Guide.
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