Hello everybody,

I've searched through the forum and some books but i can not find any answers to my question.

My problem is about many-to-many relationships which the relationship table has another primary key (other than the foreign keys) and if this primary key can not be mapped from java classes. (It's a key that's automatically given depending on the composite primary keys) Let me give an example:

_______________
|PERSON
|---------------------
|PERSON_ID (PK)
|NAME
|SURNAME
|_______________

_________________
|COMPANY
|-----------------------
|COMPANY_ID (PK)
|NAME
|ADDRESS_TEXT
|_________________

_________________
|COMPANY-PERSON
|------------------------
|COMPANY_ID (PK)
|PERSON_ID (PK)
|INDEX (PK)
|SALARY
|_________________

INDEX is just an integer that is incrementally given to a specific (COMPANY_ID,PERSON_ID) pair. SALARY, is the current salary of the person. Note that a person's salary can change within the time, so there can be more than one relationship in the same table (between person and company) so that's why index is the other primary key. (i don't want to update the salary because i am logging the history)

i have no problem with mapping many-to-many relationships to the database. But here is the case: Think about the java classes,

POJO used

/**************************************************

Person.java

public class Person {

private int id;
private String name;
private String surname;

//setters and getters
}

/****************************************************

/**************************************************

Company.java

public class Company {

private int id;
private String name;
private String address;

//setters and getters
}

/****************************************************

CompanyPerson.java

public class CompanyPerson {

private Person person;
private Company company;
private String salary;

//setters and getters
}

As you can see, index isn't in the CompanyPerson.java class. (and i don't want to put it there). So i can not map any variable to INDEX attribute of the COMPANY-PERSON table. Normally by SQL, i can easily insert it by the query :

" INSERT INTO COMPANY-PERSON (COMPANY_ID, PERSON_ID, INDEX,SALARY) VALUES (?,?, (select nvl(max(INDEX),0) from COMPANY-PERSON where COMPANY_ID=? and PERSON_ID = ?)+1,?)"

Is it possible to make it with hibernate and if it's possible how?

Hibernate version:
3.0

Name and version of the database
Oracle 10 G

Thank you for your answers..

Can you create empty setters and getters for this "field"?
And leaving out the access attribute like in:



should use the default access strategy:

Could you please explain a little more? I haven't used access attributes and can not find any example about its usage. After creating empty getters and setters (in source code) how should i map it in my own way?

Also can i do it using the formula something like that :

<hibernate-mapping>
<class name="CompanyPerson" table="COMPANY-PERSON">

......

<id name="index" column="INDEX" unsaved-value="0">
formula="(select nvl(max(INDEX),0) from COMPANY-PERSON where COMPANY_ID=? and PERSON_ID = ?)+1 />
</id>

......

</class>
</hibernate-mapping>

Thank you for your help.

Hi,

in your case if the invisible field "index" is part of the primary key my
last suggestion will not work, since the hibernate session cache needs
the all primary key fields. What about an id class as
explained in section:

9.4. Components as composite identifiers

Sorry for my late response, i had lots of work to do at the weekend so i could not use the internet.

Thank you for your help but i have another question. composite identifier may solve my question about mapping but how can i define my formula for the index attribute?