Help With Inheritance

[rread]

I am triying to define a table structure

with the following logic.

If i have a DataType By example Person,

a person can be one of 3 types of persons

he can be a costumer or a material supplier.

the problem is i want to have only on register of person,

but a person can be either a costumer and/or a supplier,

meaning he can be both.

How can i represent this in a object structure without

the use of descriminator?

so that in the end i can have something like the code bellow.

@Entity(name="TPerson")

@Inheritance(strategy=InheritanceType.JOINED)

abstract class Person {

    String id;

    String name;

}

@Entity(name="TCostumer")

class Costumer extends Person {

    Date birthdate;

}

@Entity(name="TSupplier")

class Supplier extends Person {

    String companyName;

}

[rread]

no one has any ideas?

[nbelaevski]

Hi Felix,

This forum is dedicated to RichFaces, so I'm going to move this thread to Persistence forum.

[wdfink]

I'm not sure about your problem

If you implement like this and create two persons (one as supplier and one as customer) they will be different, but if I understand right you want to achieve that a single person is a customer AND a supplier right?

[rread]

yes

TPerson

id name

1  xxxxxxxx

TCostumer

id  birthdate

1   xx/xx/xxxx

TSupplier

id  companyName

1   xxxxxxxxxxxxx

[wdfink]

Mmm,

maybe two tables related to TPerson with a 0..1-1 relation might be a solution.

And TPerson contain a method isCustomer() { return custAddon != null } => custAddon.getBirthday()

And the same for supplier.

[rread]

It seems the problem is in the mapping, cause acording to recomendations, each record of TPerson should have a relations ship with only one of the 2 tables(TSupplier or TCostumer) exclusively, and this because when the SQL Query is generated is contains and explicit INNER JOIN.

A Examplo of the problem :

Lets Asume a ORACLE 11g database,

there is a Record of TCostumer with id 1, and there still no record in TSupplier.

we would have

TPerson

id name

1  xxxxxxxx

TCostumer

id  birthdate

1   xx/xx/xxxx

TSupplier

id  companyName

so you have a registerd client, and this client is not yet a supplier.

But it so happen that one day this client opens a bussiness and

has to be register as a supplier with out lossing his rol as client.

So now that we understand the problem we proceed:

1.- We check if there exists a supplier with id 1, at this moment

the Generated SQL would be a

"Select p.id, p.name, s.companyName from TPerson p,TSupplier s where p.id=s.id",

in this case the result would be that it does not exists, cause its a inner join and there

does not exists a record in both tables.

2.- even so we can verified that there exits a person, in this case the SQL would

be something like

"Select p.id, decode(p.id,s.id,"Supplier.class",c.id,"Costumer.class")  from TPerson p, TSupplier s, TCostumer c where p.id=s.id(+) and p.id=c.id(+)"

and the result would be that the record is found in TCostumer,

but the requested entitie was TSupplier wich would result in a type compatibility error, and that would happen

cause we where triying to look for a abstract Person and than a LEFT JOIN is applied for both tables (TCostumer, TSupplier)

3.-But even so, we insist and we try to create a new Supplier, we call new Supplier(), we do the required sets,

and the we execute persist. the result would be a duplicated PK Error, that because we where triying to insert into

both tables, (TPerson and TSupplier), considering that acording to step 1 that entity does not exists.

Hopes this explains the problem a little more clearly.