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From Larry Schuler <larry...@yahoo.com>
Subject Re: Mapping workbench, finally
Date Tue, 22 Apr 2003 15:54:42 GMT
Florian,
  Since I'm one of the "perpetrators" I'll respond with my needs.

We have a project with a pre-existing database, we also have a crufty
tool that takes a UML model and generates java code. So, my role is to
create a persistence layer that maps the classes to the tables. For this, I 
needed a tool that would:
  1. Display a list of tables in the db
  2. Display the list of java classes
  3. Pick a class and a table and create a map for that pair by
     identifying which attributes matches which column. It should be
     able to map PK, prmitives, Object references, and Collections.
  4. Some nice features are saving the xml mapping as a single
     file, or one file per class.
  5. Highlighting classes/tables that are unmapper, or partially
     mapped (the tool I wrote doesn't do this)
  6. "Re-integrate" the java classes or database tables if either
     of them change (another hopeful)
  7. Customize the properties for a specific mapping (down to
     attribute-column level)

The tool I wrote does all but 5&6 which I may end up adding shortly. For me,
this tools is going to save me a lot of time and effort *right now* which
is why I wrote it.

I can certainly see other needs, and in fact, I think if this current
project works out, we may redo some other systems which wouldn't have
a pre-exisiting db limitation, so I could see another use. Scenario two, the ideal:

  1. Suck in a UML file
  2. Spit out java classes, a mapping file, and the DDL to create the database.

But, I have not researched options on this, there may be a tool that does
this right now.

  A slight alternative would be
  1. Analyze java source files
  2. Create a mappping file and a database schema to match up to the
     classes.

Just my thoughts,
--Larry Schuler

BTW, I didn't realize the Reversedb2 was there, my loss...


Florian Bruckner (apache.org) wrote:
> Hi,
> 
> I am crossposting this intentionally to users AND dev-list as I hope I can
> get some more attention for this message. This is just meant to start the
> discussion, please let us discuss these matters on the dev list.
> 
> Recently a some graphical tools popped up that all claim to solve specific
> problems concerning repository mappings. It is good to see that OJB has a
> growing user base and that there is increasing willingness to contribute to
> the success of OJB. On the other hand it makes me somewhat sad that these
> effort are all but coordinated. For example there is a plugin for eclipse
> that is based on reversedb (see below), Mathias undoubtedly put in a lot of
> effort to fix bugs and make the classes work for his purpose. But neither
> have any bugs ever been discussed on any public mailing list nor have the
> bugfixes made it back to the codebase of reversedb. The result is lost
> effort on both sides and software that is less functional than it could be.
> 
> OJB currently has (and has had for a long time now) two flavours of a
> mapping workbench. Reversedb is a simple (slow and buggy) application to
> read a database schema and generate XML and java classes. Reversedb2 is a
> rough prototype for a mapping workbench with a better design than reversedb.
> Both applications suffer from the fact that design and implementation have
> been made by a single person (me). The design is possibly even broken in a
> way that makes it impossible to implement certain requirements.
> 
> I understand that it is a problem for a lot of people to contribute to a
> piece of software where they have not been able to contribute during the
> design phase and when they think they could have done better. Let's throw
> away all we have and start over again.
> 
> This email should be seen as a call for a discussion. Let's discuss what the
> requirements to a mapping workbench are, let's discuss the goals and how
> these goals can be achieved, let's discuss who can take which role in such
> an effort, let's discuss a design and let's make the best mapping tool
> possible. And let's combine our efforts.
> 
> regards,
> 
> Florian
> 
> 
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