[Objectbridge-jdo-dev] RE: default mapping rules (Brian Westrich)

[Brian W. <bw...@mc...>]

Oops, noticed my last post contained non-ASCII characters which
weren't very readable. Below is a cleaned up version of the
original post.

Also, since posting I noticed someone mentioned the need to
map relationship related fields. The Forte tool does this as
well. The convention it uses is:

For fields that map to one instance of another class:
class name starting with lower case letter (e.g. myClass)

For fields that map to 0-n instances of another class:
class name starting with lower case letter +
"CollectionFor" + primary key property(ies)
(e.g. if MyClass has a primary key field named myId, and the
table mapped to MyClass has a table named MY_DETAIL_CLASS, the
relationship field would be named myDetailClassCollectionForMyId)

The above convention for 0-n is the 'complex cardinality'
convention. One can also choose a 'simple cardinality', which
leaves the "ForMyId" part off the name.


-- Brian

> Hi ojb developers,
>
> It=92s great to learn of your efforts to write an open-source JDO
> product! Having used the free JDO stuff bundled with Forte for
> Java 3.0, I=92m smitten by the benefits of JDO, but since JDO is
> discontinued in the next release of Forte (now called Sun ONE),
> I=92m looking for a replacement. I can=92t help out much with ojb
> right now, as I=92m knee deep in a couple projects until at least
> mid-Summer. So if you don=92t mind I=92ll mostly just keep reading
> the dev mailing list.
>
> Having said this... I do have one possible small (code)
> contribution. As you consider default mappings, you might
> consider using the conventions used by the schema reverse
> engineering tool bundled with Forte for Java (which generates
> classes from an existing schema). This converts database schema
> using underscores for word separators (e.g. MY_TABLE,
> MY_COLUMN) into Java-like mixed case names (e.g. MyClass,
> myProperty). This convention allows one to quickly set up JDO
> objects to talk with an existing database schema without any
> underscores in Java class names. If ojb used this convention,
> ojb users with existing databases could use the Forte tool to
> generate initial versions of their classes. I know such a
> simple mapping (table to class, column to property) is
> simplistic, etc., but it sure is a great way to get started.
> Another option, if you=92re not comfortable with this particular
> convention, is to add an extension tag to the *.jdo file
> (perhaps at the package and/or class level) indicating that
> this convention was in use. If you=92d like, I=92d be delighted to
> contribute code and JUnit tests to the project that do these
> conversions.
>
> I look forward to seeing your thoughts on the list related to
> this idea on default mappings.
>
> Keep the faith!
>
> -- Brian
>
> Brian Westrich
> McWest Corp.
> bw...@mc...
> 612-508-1827
>