Help with mapping to legacy db

tergus · **Posted:** Fri Mar 18, 2005 1:36 am

Hibernate #: 3 (any)

I have a rather unique situation where the database schema that I have to work with doesn't seem to be covered in any examples/doco. I hope I explain this well enough.

The sample schema that I have is as follows:

Code:

table code
(
  code char 4
  type  char 4
  data  varchar 100

  PRIMARY KEY(code,type)
)

table example
(
  data1 ...
  data2 ...
  code char 4
  ...
)

As you can see from the 'example' table, to get the data from the 'code' table you need both keys. In the legacy application this is done programatically in the sql:

Code:

select example.data1, code.data
from example, data
where example.code = code.code
and code.type = 'TYPE'

Is there anyway to do this in the hibernate mapping file (which would be the preferred way) as opposed to programatically. If anyone could help me out on this, it would be much appreciated.

Dan Washusen · **Joined:** Sat Sep 25, 2004 12:42 am **Posts:** 27

I don't think I really understand the relationships between the two tables from the details you have given, but, check out the "Components as composite identifiers" section of the hibernate documentation.

eg. The collection of OrderLines in Order would use:

Code:

<set name="orderLines" inverse="true">
    <key>
        <column name="orderId"/>
        <column name="customerId"/>
    </key>
    <one-to-many class="OrderLine"/>
</set>

Maybe you could include the mapping you have so far, or a simple ER diagram...

max · **Posted:** Fri Mar 18, 2005 2:37 am

if looks like you need a combination of components and formula.

and if you look into formulajoin test in Hibernate 3 that *might* also help you.