<cocoon-user-note>
To Cocoon users: Sorry for the off-topic post.
This is just a heads up to let you know what _may_
be coming and to solicit your lobbying efforts for
the Torque changes I am proposing below.
</cocoon-user-note>
Dear All,
I'd like to have some new functionality in Torque. My
ultimate goal is to implement the enhancements necessary
to make Torque a useful component when developing with
Cocoon.
<disclaimer>
I'm not hung up in implementing the changes exactly
as suggested here. I've written the following mainly
to clarify my ideas and solicit better suggestions
from those who know more. That said, I've tried to
keep things simple by separating my requirements from
the solution and suggesting a 'small-footprint' change
that I can quickly get up and running.
I just want a solution for my requirements and I'm
willing to write and test the code and DOCUMENT
whatever we collectively decide to do. But, barring
other suggestions, my analysis thus far shows that
I do require changes to Torque (and I'm not a Torque
commiter).
On the non-technical side, I'd like the community,
particularly the Cocoon users (who will get a new tool
for their toolbox), to share the benefits. After all,
the Torque-ers have already helped me.
</disclaimer>
1. REQUIREMENTS
===============
1.1 Populate Torque objects, e.g. objects which extend
BaseObject, automatically from a Map or Hashtable.
E.g.:
// users is an instance of a Users Torque object
// generated by Torque.
users.populate( myHashFromMyCgiInput );
if ( user.isValid() ) { // isValid is business logic
users.save();
} else {
throw new BadUserInputException(); // or whatever..
}
Ideally the populate() method would accept String
representations of fields and convert them to the
appropriate native types (as well as accepting native
types).
1.2 Allow Torque objects to emit SAX events to a
Content handler.
Note: most Cocoon processing is done via SAX events.
// myContentHandler is a Cocoon transformer that
// ultimately transforms it's input into fancy
// HTML suitable for web browser presentation.
// It has been opened and a document has already
// been started
myUser1.toXml( myContentHandler );
myUser2.toXml( myContentHandler );
myCompany1.toXml( myContentHandler );
// ..etc.. until done.. then close the document.
The toXml() method merely emits the tags and content
associated with to it's database record. E.g. the
table name '<user>' and the contained fields,
'<Userid>1</Userid><Username>joe</Username>' etc..
Note: If you accept this, then you'll get XML as
Strings more or less for free. (And you'll get free
Steak Knives too.. :)
2.0 POSSIBLE SOLUTION
=====================
<another-disclaimer>
Read the first disclaimer again: I'm open to other,
better solutions.
</another-disclaimer>
2.1 Populate()
With a bit of Java (and personal :) introspection and some
helpful suggestions from the list members, I feel I can
implement the populate method. The tricky part will be
getting all the type conversion working.
This task would be made MUCH easier if there were a
method getFieldNames(), that returns null (or throws an
exception) in BaseObject. It would be over-ridden by all
the Torque generated classes).
This would allow applications to use Torque objects in a
generic way. They could simply iterate over all the fields,
using BaseObject's (overridden) getByName method.
2.2 Sax events
Given the getFieldNames method in BaseObject, it becomes
a trivial exercise to implement the SAX event generation
directly in BaseObject. It is would also be trivial to
implement a toXml method, that returned the XML as a
String. (..and you'd get free Steak Knives too. :)
The only problem is to get the table name (for placing in
the top-level XML tag). The easiest solution would be to
add a null (or exception-throwing) method getTableName to
BaseObject, which would be overridden by the generated
Torque objects.
Note: since I pan to use Cocoon, I have no need of filtering
or forcing the XML to conform to any particular layout.
Cocoon allows me to easily use XSLT to perform any required
transformation(s).
3.0 SUMMARY OF CHANGES
======================
3.1 Add to BaseObject.java:
public List getFieldNames() { return null; }
public String getTableName() { return null; }
They could alternatively throw a 'not implemented'
exception the way getByName currently does.
void populate( Map or Hashtable ) { ... }
void toXml( ContentHandler ) { ... }
String toXml( ) { ... }
or toXml( Writer ) { ... }
I'll supply tested code with Javadoc for these methods.
3.2 Add to Object.vm:
public String getTableName() { return "$table.Name"; }
I'll need to test to ensure that the Torque/velocity variable
name is correct.
3.3 Collect the free Steak Knives :)
Sorry, but we're all out of Steak Knives :(.
..but I will write a few paragraphs of documentation for
the Torque web site and some Cocoon Wiki documentation when
I get this working with Cocoon. (That's BETTER than steak
knives, right? :)
4.0 AN APPEAL
=============
4.1 Is there a Torque committer willing to 'sponsor me'?
No, not to sponsor me to become a commiter, just to commit
the changes.
4.2 I'll supply the changes in whatever format is easiest.
Best wishes and thanks in advance (especially for reading
this far),
Alan.
P.S.
<thanks>
Nothing happens in a vacuum: Others have helped. In particular:
Michael Bain - For sharing your introspection based solution.
Gareth Boden - For sharing your Betwixt based solution and
giving me a bunch of insights.
Without your efforts, I would have been stuck. Thanks guys!
</thanks>
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