seam generate entities for many-to-many relationships

[wouterhartog]

I have a MySQL database with 3 tables:

-User

-Role

-UserRoles

The UserRoles table is just there to enable the many-to-many relationship between User and Role.

When I run generate entities, it creates three different entity classes, while I only expect two:

- one for the User with a @ManyToMany annotation pointing to the Role table with joinColum = UserRole

- one for the Role (with or without a ManyToMany annotation pointing to the UserRole table)

Instead it also creates an entity class for the UserRoles table, which I don't need / want, and the relation to the UserRole table is a OneToMany relation.

Is there any way you can influence / setup the behavior of 'generate entities' to look at the many-to-many relationships, or is this always something you have to change manually in the entity classes later, after 'generate entities' did its work?

Versions:

- MySQL 5.1

- Seam 2.2

- Jboss Tools 3.0

- Eclipse 3.4.2

[wouterhartog]

Found the solution:

I had to define my UserRole table different.

I had one UserRoleID column as the primary key, and the userId and roleId as just FK to the other tables, like this:

userRoleId (PK)

roleId (FK)

userId (FK)

When I changed the table structure to this (removed the original PK column):

roleID (PK, FK)

userId (PK, FK)

seam generate entities worked as I wanted to: on the Entity class User, I had a @ManyToMany annotation, linking to the Role table, using the UserRole table as the joinTable.

a great tool!

[maxandersen]

Yes, your solution is correct since otherwise we just see the tables are three related entities. No way to detect the many-to-many.

But to answer your question about convincing/controlling seam-gen (or rather hibernate tools) beyond what is in your database lookup rev-eng.xml in the documentation or google

[goschan]

Hello,

yes the seam gen generates only two entity, but in the xhtml (supplier.xhtml in my case) view file, I have this :

<h:outputText value="There are no lkSupplierAddresses associated with this supplier."
                   rendered="#{empty supplierHome.lkSupplierAddresses}"/>

<rich:dataTable value="#{supplierHome.lkSupplierAddresses}"
                       var="_lkSupplierAddress"
                  rendered="#{not empty supplierHome.lkSupplierAddresses}"
                rowClasses="rvgRowOne,rvgRowTwo"
                        id="lkSupplierAddressesTable">

lkSupplierAddresses is my table with the two IDs as a primary key (suppId and addId), when I try to access this outputText, or dataTable I have this exception :

16:29:15,885 ERROR [viewhandler] Error Rendering View[/Supplier.xhtml]
javax.faces.FacesException: javax.el.PropertyNotFoundException: /Supplier.xhtml @66,77 rendered="#{empty supplierHome.lkSupplierAddresses}": Property 'lkSupplierAddresses' not found on type com.orderform.session.SupplierHome_$$_javassist_seam_11

So  there is a problem in the generation of the xhtml files.

Do you know is there is a fix for the generation files ftl ?

Thanks, Benjamin

[maxandersen]

That is better asked at the seam forums since we are simply using the seam-gen templates here - but I don't believe seam-gen ever supported many-to-many generation fullly.