Data in join table apart from the foreign keys using EJB2.0 2004-03-03 - By Markus Fuchs
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Hi Vijith,
Your problem sounds like you want to have attributes on a relationship mapped to
a join table. This can be handled in the following way:
* You need to map TableC as a separate entity, say EJB3.
EJB3 will have two collection relationship fields, say EJB1s and EJB2s.
EJB1 and EJB2 will have object relationship fields to EJB3.
* To establish a relationship between EJB1 and EJB2, set the relationships
between EJB1 and EJB3 and EJB3 and EJB2 in ejbPostCreate.
HTH,
-- markus.
>
> Hi All,
>
> I have a scenario like this
> -- ---- ---- ---- ---- ------
>
> TableA (col1 PK)
>
> TableB (col2 PK)
>
> TableC (col1 , col2, col3)
> -- ---- ---- ---- ---- ------
> (Col1 + col2) composite PK
> Col1 is FK(TableA)
> Col2 is FK(TableB)
> Col3 is a normal column
>
> -- ---- ---- ---- ---- ---- ---- ---
>
> Now I have designed the EJB like this
>
> EJB1 (Entity Object for TableA)
> EJB2 (Entity Object for TableB)
>
> There is a many - many relationship between EJB1 and EJB2 with TableC as
> join table.
>
> I'm following the SessionFacade pattern. In the Session Bean , I create
> the entity for EJB1 and create the Entity for EJB2. In the CMR setter of
> EJB1, i associate the EJB2,(though after adding it to a collection),
> which populates data to TableC.
>
> In this way, the data is inserted into TableA, TableB and TableC like
>
> Table A
> -- ----
> col1
> ----
> 1
>
> TableB
> -- ---
> col2
> ----
> 1
>
> TableC
> -- ---
> col1 col2 col3
> -- ---- ---- ------
> 1 1 null
>
> My requirement here is to insert data to col3 in the same transaction ie
> the data should get populated in the same transaction that inserts data
> into col1 and col2 of TableC.If the validation for col3 fails, all
> inserts should be rolled back.
>
> I tried this appraoch. I created EJB3 which maps to TableC and performed
> the following steps.
>
> Steps
> -- --
> 1) In session bean, create EJB1 and get the reference to
> the EJB1object
> 2) In session bean, create EJB2 and get the reference to
> the EJB2object
> 3) create new vector with EJB2object as an element.
> 4) On EJB1object , call setCMREJB2(vector);
> (The above series of steps inserts data in all the table except for col3
> in TableC)
> 5) Try to get the handle for the EJBObject for table3
> using findByPK(new PK(col1, col2))
> 6) But this fails as the previous transaction is not
> commited and findByPK fails. So Im not able to call
> setter for col3 in EJB3.
>
> Any suggestions :-)
>
> Thanks
> Vijith
>
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