I am having trouble understanding an error I am getting while trying to set up a one-to-many association in Hibernate 3.1.

My database consists of three tables:



This is intended to represent a structure between objects such as: Group--(0..1)--------------------(0..*)--Item

I have used the hibernate_reference.pdf as supplied in the download as guidance, and I thought the scenario as covered ing section 7.5.1 one to many / many to one matched my problem. As a result I have set up my hibernate mapping as follows:

<hibernate-mapping package="spike.grouping">
. <class name="Group" table="tblGroups"
. . ....
. . ....
. . <set name="items" table="tblGroupings">
. . . <key column="id_g" />
. . . <many-to-many column="id_i" unique="true" class="Item"/>
. . </set>
. </class>

. <class name="Item" table="tblItems" dynamic-update="true" optimistic-lock="version">
. . ....
. . <join table="tblGroupings" inverse="true" optional="true">
. . . <key column="id_i"/>
. . . <many-to-one name="Group" column="id_g" not-null="true"/>
. . </join>
. </class>

</hibernate-mapping>


However, when I run my unit tests I get the following error which I do not understand, (I've cut the bulk of it out, just listing line details, I can give the fill stack trace if needed:




Obvisouly it's informing me that I've done somthing wrong in my mapping, but I do not undersand which bit, if any it is telling me is wrong.

Any help would be very much appreciated.

Ok, as always the process of writing out the question sheds a little more light.

The problem was that I had other elements in my mapping along the lines of:

<hibernate-mapping package="spike.grouping">

. <class name="Item" table="tblItems" dynamic-update="true" optimistic-lock="version">
. . ....
. . <join table="tblGroupings" inverse="true" optional="true">
. . . <key column="id_i"/>
. . . <many-to-one name="Group" column="id_g" not-null="true"/>
. . </join>

. . <set name="someProperty"...>
. . . .......
. . </set>
. </class>
</hibernate-mapping>

E.g, <set... defines AFTER the join, this does not work and was the cause of my problem.

It was solved by moving the <join .. to the bottom of the class definition. I thought the class mention in the exception trace was refering to the 'class' element of the <many-to-many> tage of the Group mapping.