Mapping two tables to one object

vihung · **Joined:** Tue Apr 18, 2006 4:54 am **Posts:** 9

Hibernate mapping allows you to define two objects coming from the same table

For example, I can easily have two POJOS, say, Person and Name

Code:

Person
------
dateOfBirth: Date
name: Name
...
------

and

Code:

Name
------
firstname: String
lastname: String
------

mapped to one table

Code:

PERSON
------
PERSON_ID    INTEGER    PRIMARY KEY
DATE_OF_BIRTH    DATETIME
FIRST_NAME    VARCHAR
LAST_NAME VARCHAR
-----

The question is, if I have a complex (e.g. long, but flat) POJO, can I map it across two tables.

For example, one POJO called Person

Code:

Person
------
dateOfBirth
name: Name
firstname: String
lastname: String
...
------

mapped to two tables PERSON and NAME with the same primary key

Code:

PERSON
------
PERSON_ID    INTEGER    PRIMARY KEY
DATE_OF_BIRTH    DATETIME
-----

and

Code:

NAME
------
PERSON_ID    INTEGER    PRIMARY KEY
FIRST_NAME    VARCHAR
LAST_NAME VARCHAR
-----

Hibernate version: Any

huangjd · **Joined:** Wed Jun 21, 2006 10:08 am **Posts:** 26

In short, no.

You can come up with a clever strategy to have a one-to-many mapping. Such that 1 person can have many names, such as a rock star having aliases or a person having nick names.

Hope that helps.

vihung · **Joined:** Tue Apr 18, 2006 4:54 am **Posts:** 9

That is a shame.

The reason I ask is because I am trying to figure out the best way to migrate an application from ATG Dynamo (http://www.atg.org) to a Spring and Hibernate based platform, and their ORM framework (ATG Repositories) does allow you to do this.

Perhaps one way to do it would be to use a view in the database to join the two tables - thus presenting a single 'table' for the Hibernate mapping.

Quantum5 · **Joined:** Fri Jun 09, 2006 8:03 am **Posts:** 12

If your person didn't have a name it could easily be done with the join tag, here is a good tutorial/example:
http://blog.exadel.com/?p=16 (Scroll down to The Joined Tables Pattern)

If name needs to be in there, you might be able to use composite patterns that are talked about in the reference documentation. I haven't really used composite classes so I don't know.

vihung · **Joined:** Tue Apr 18, 2006 4:54 am **Posts:** 9

Sorry. That was a typo. The POJO does not need a name property if it has firstname and lastname

e.g. it would be

Code:

Person
------
dateOfBirth
firstname: String
lastname: String
...
------ 

and not

Code:

Person
------
dateOfBirth
name: Name
firstname: String
lastname: String
...
------ 