project.xml is a jelly script?

[Jason Dillon]

Hello, the website says that "project.xml form, is now processed as a 
Jelly script " 
(http://maven.apache.org/reference/user-guide.html#POM%20Interpolation 
) but it does not appear to be having like it is a jelly script at all.

Is the user guide not valid?  Is there a special property to enable 
this?  I have looked over the source and it does not appear that any 
jelly fluff is done to the project.xml file.

IMO I think that it would be very beneficial if it was a jelly script 
so that Maven in general is more flexible.  I understand not wanting to 
put much logic into the project.xml, but it would make management of 
large projects much easier.

Specifically I was looking for a way to define common dependencies for 
a large project (Apache Geronimo) so I could better manage version 
numbers of the dependencies.  I did not wish to put all of the depends 
into a parent project as that would force each child project to have 
additional dependencies on its classpath which might not be a good 
thing, nor do I want each and every module to try to download 
SNAPSHOTS, especially if they do not even need that depend.

So I thought about using properties like 
'dependency.commons-logger.version=1.0.3' and then specify the property 
as the content for <version/>, which works fine if the property is 
defined in the child modules project.properties, or if the property is 
in the parent and the child is always invoked through the reactor.  
This is not the case with Geronimo, so this method fails.

James and I were chatting about this a tad... I was under the 
impression that I could use jelly in project.xml (drawn conclusion from 
web page and some bad tests I made).  He suggested using <x:parse 
xml="../../dependencies.xml"/> and then selecting out dependencies by 
name and then copying them into the project.xml.  I think this would be 
very useful and shows where project.xml as a jelly script would be 
desirable.

I think this is a good idea, but wanted to hear what you guys have to 
say.

Also I was talking to James about the problem of versioning 
dependencies in general and how it would make sense if Maven supported 
more symbolic names (similar to SNAPSHOT) but which could point to the 
latest stable release.  It probably makes sense to provide some sort of 
version alias mechanism, as it becomes problematic to effectively 
maintain version numbers in a large project.  Take Maven for example, 
there are a few plugins which use different yet compatible versions of 
dependencies, which only results in additional overhead.  If all 
plugins are compatible with a specific version, then it would make 
sense for them to all use that version.

Anyways I have been up for way too long, it was light when I woke up 
and it is light again, so I am gonna crash now.

Cheers,

--jason