mapping unidirectional relation with parameterised compound

[andy.2003]

Hello,

I need some help for map the follwing relations with ejb3:

|-------------------| |--------------------|
|Product | |Description | |-------------------|
|-------------------| |--------------------| |Languages |
|product_id:int (PK)|----->|product_id:int (PK) | |-------------------|
|... | |language_id:int (PK)|<----|languga_id:int (PK)|
|-------------------| |... | |... |
 |--------------------| |-------------------|

I need a method for getting the Productdescription for a specified language
like

public Description getProductDescription(int pLangugeId)

For me the problem is to set up such a method. I get an error when I try to set up a relation with a parameter (the languges_id isn't stored in the Product Class and it's an unidirectional relation!).

Can anybody give me a hint how to solve this problem?!

Thanks Andreas

[andy.2003]

tile was cut:
mapping unidirectional relation with parameterised compound foreign keys

[cyril.joui]

Hello,

Did you try to map your Collection and after add your getProductDescription(int pLangugeId) (and make a while to search the good description for the specified language ?)

It's not a very clean solution.

I will search for cleaner solution ;)

Good luck

@soon

[andy.2003]

Yes, I managed to set up a OneToMany relation like:

public Set<Description> getDescriptions();

but this is not what I'm searching for. I dont want to fetch all description-entries for an product, I only need the entry for the specified language.

[cyril.joui]

I think you must use a Session Bean Façade to initialize your Description (by an EJB QL).

Why do you think about it ?
I think you have already a session bean (to represent a DAO or a service) ?
So it would be easy to set the good description for the current language of user for example.

[andy.2003]

I dont have a session bean at the moment (but should be no problem)

Is there no way to get a method in the Product Class to get the description for the specified language?

I don't understand how you want to "initialize" the Description ...
Do you mean that I should add a NamedQuery like this:

@Entity
@NamedQuery(name="getProductDescription", queryString="Select d from Description d where d.language_id >= :language_id")
public class Description{
 ...
}

But in this case I dont have the current Product...

If I choose this:

@Entity
@NamedQuery(name="getProductDescription", queryString="Select d from Description d where d.language_id >= :language_id and d.product_id >= :product_id")
public class Description{
 ...
}

I need both Id's, hmmm, this should be possible.

But there is the next problem: If I set up the Entity like this:

...
@Id private int product_id;
@Id private int language_id;
...

the table is set up wiht only 1 PK (e.g. product_id). I thought I only need a PK-Class for complex PKs (two integer seems not to be complex)

So if I have to set up a PK-Class, can I use the NamedQuery as listed above? (and do I need a PK-Class for two int-values?)

Thank you so far!
Andreas

[cyril.joui]

Did you try to make 2 relationships in your description POJO ?

In hibernate there was ternary Associations : http://www.xylax.net/hibernate/ternary.html

I haven't tried this but I think you can define the two relationship and set the primary key with JoinColumn annotation.
I am not sure !
Look at this :
http://www.goobsoft.com/resin-doc/ejb3/cmp-table.xtp#@Entity
At the @JoinColumn.

If you try it can you tell me if it works ?

Thanks.

[andy.2003]

I want a unidirectional access to the Description - Class, this means, in the Description - Class there is no variable storing the Product, so I cant create a ManyToOne mapping.
If I setup following mapping in the Product Class I get only one PK in the Description Table:

@OneToMany
public Set<Description> getDescriptions(){
 return ivDescription;
}

...

[cyril.joui]

Yes, I see...
You try to use an existing DataBase ...

I saw that :
http://jroller.com/page/raghukodali?entry=ejb_3_annotations_for_mapping

I think it can help you.