After the recent refactoring of Cocoon where part of cocoon-core is
moved to the new cocoon-bootstrap, we have two packages: o.a.c.servlet
and o.a.c.util, that are split into two blocks. This means that we
cannot work on Cocoon3 anymore.
With OSGi, dependencies are at the package level. If several bundles
(blocks) provide the same package the framework will chose the package
from one bundle and ignore the rest of the implementations of the
package (actually, several versions of the same package can be used at
the same time but that is not relevant for the current issue).
This means that it doesn't work to have a package split so that some of
the classes in the package is in one bundle and some other is in another
bundle (in R4 there are mechanisms two handle split packages, but it is
not recommended and increase the complexity considerably).
We need to find a solution for this and also decide what conventions we
should have for package naming and what we use packages for. OSGi (and
Java in general AFAIU) is based on the concept that a package contains a
number of classes that works closely together to provide some well
defined functionality. In Cocoon we sometimes use packages in this way,
but also quite often based on some kind of similarity, e.g.
o.a.c.transformation. The later use of packages, doesn't work well with
modularization. I recommend you to read Peter Krien's blog about why
packages are the right level of modularization:
http://www.aqute.biz/2006/04/let-us-not-make-same-mistake.html.
We have discussed package conventions for blocks before and
o.a.c.<blockname> as package prefix for a block seam to be a reasonable
convention, that package name clashes between block communities.
For cocoon-bootstrap I would suggest that we keep o.a.c.classloader as
is, as the whole package was moved from cocoon-core and as it doesn't
have anything with bootstraping to do AFAICS. o.a.c.servlet can go to
o.a.c.bootstrap.servlet (we could possibly keep and deprecate
o.a.c.[BootstrapClassLoaderManager|ParanoidServlet] in 2.2 and just let
them extend the moved classes in o.a.c.bootstrap.servlet). o.a.c.util is
most complicated, ClassUtils could go back to cocoon-core as it isn't
used in cocoon-bootstrap, it is less clear what we should do with the
WildCardHelper.
WDYT?
/Daniel
- Blocks and packages Daniel Fagerstrom
-
