RE: [eclipselink-users] customize OneToMany Mapping

[Robert Wimmer <seppwimmer@xxxxxxxxxxx>]

Hi Tom,

thanks for your response

>
> Can you provide a more in-depth description of the mapping you are trying to
> create between target_table and table_between. i.e. The classes involved and
> the relevant instance variables and the tables involved. The reason I ask is
> that based on your initial description, I was under the impression this is a
> typical 1-M mapping, but it seems it may not be.
>

public class Contact {
   Long id;
   String type,label;
}

public class Address {
     Long id;
     String firstname,lastname; 
     List <Contact> contacts;
}

The Tables look like this (PostgreSQL Syntax)

CREATE TABLE contact (
   id BIGSERIAL PRIMARY KEY,
   TEXT type,
   TEXT label
);

CREATE TABLE person (
   id BIGSERIAL PRIMARY KEY,
   TEXT firstname,
   TEXT lastname
);

CREATE TABLE contact_person (
   contact_id BIGINT NOT NULL REFERENCES contact(id),
   person_id BIGINT NOT NULL REFERENCES person(id)
);

So the query for the contacts of  a person  i have to do the following

SELECT * FROM contact c
JOIN contact_person cp ON cp.contact_id = c.id
WHERE cp.person_id = ?

This is indirection is used really often and it is some sort of a design standard (the reason is you can establish new relationships between tables without changing the table definition itself).

So how can I desribe this kind of relationship with the eclipselink api ? Is it possible with a OneToMany mapping

         OneToManyMapping mtm = new OneToManyMapping();
         mtm.setAttributeName("contacts");
         mtm.setReferenceClass(Contact.class);
         ??? mtm.addTargetForeignKeyFieldName("contact.id", "contact_person.contact_id");
         ??? 
         ??? mtm.dontUseIndirection();
         personDescriptor.addMapping(mtm);

Thanks in Advance Sepp

P.S.: I also dont know who to define Postgres Secquences in eclipselink and find no help in the Web for it. Any Idea ?


 

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