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Help on one-to-many relation.

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joshi.sujit

Post subject: Help on one-to-many relation.

Posted: Thu Jun 19, 2008 1:01 am

Newbie

Joined: Thu Jun 19, 2008 12:37 am
Posts: 1

Hi All,

I am new to hibernate.

We have a DB like this.

Companies
========
company_id(PK),
parent_company_id,
status,
...

User
=====
user_id(PK),
company_id,
....

contacts
======
contact_id,
firstname,
lastname,
companyname,
ref_object_id,
ref_object_name,
.....

Contact information for company or user will be stored in contact table with respective primary key values in "ref_object_id" column and table name in "ref_object_name" column of the contacts table.

NOTE: ref_object_id can have similar value in it for different table, means
for company 1, ref_object_id will have "1" with ref_object_name having "Companies" in it, at the same time for user 1, ref_object_id will also have "1" with ref_object_name having "User" in it.

One company/user can have multiple contacts which we have to take as a set of contacts.
How can i get the company/user contact information using set and one-to-many with contacts? because set will have one key column(which is ref_object_id in contact table). With only one key we can not relate to contact table from company/user.

Please help me in this....

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Joerg.Schoemer

Post subject:

Posted: Thu Jun 19, 2008 4:58 am

Newbie

Joined: Thu Jan 03, 2008 8:39 am
Posts: 5

Hi,

try this

Code:

@DiscriminatorColumn(name = "ref_object_name")
abstract class Contact {
    String name;
    ...
}

@DiscriminatorValue(value = "User")
UserContact extends Contact
{
    @ManyToOne
    @JoinColumn(name = "ref_object_id")
    User user;
}

@DiscriminatorValue(value = "Companies")
CompanyContact extends Contact
{
    @ManyToOne
    @JoinColumn(name = "ref_object_id")
    Company company;
}

class User {
    @OneToMany(mappedBy="user")
    Set<UserContact> contacts;
    ...
}


class Company {
    @OneToMany(mappedBy="company")
    Set<CompanyContact> contacts;
    ...
}

Best regards
Joerg

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