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From Ralph Goers <ralph.go...@dslextreme.com>
Subject Re: [Commons Wiki] Update of "MavenGroupIDChange" by sebbapache
Date Sat, 13 Nov 2010 15:09:12 GMT
This is a great post.  Personally, I think the need to do this is completely caused by Maven
and I've been discussing this with them for years.  I will be writing up a proposal on the
Maven wiki which would eliminate the need to keep renaming packages and artifacts.  Instead,
artifacts would contain additional metadata they could use to describe things like the version(s)
of the API that they support, configuration versions, and other attributes that might affect
the user of the artifact. Then users of the artifact, in addition to specifying the groupId
and artifactId would specify the attributes and their versions that they require. Maven could
then use this information to insure that only a single version of the artifact is present
and that it meets the requirements of all the projects that list it as a dependency.  If multiple
projects specify the artifact with different metadata that can't be resolved by any available
version of the artifact then the build would fail.

Ralph

On Nov 13, 2010, at 6:32 AM, Apache Wiki wrote:

> Dear Wiki user,
> 
> You have subscribed to a wiki page or wiki category on "Commons Wiki" for change notification.
> 
> The "MavenGroupIDChange" page has been changed by sebbapache.
> http://wiki.apache.org/commons/MavenGroupIDChange?action=diff&rev1=3&rev2=4
> 
> --------------------------------------------------
> 
>  === Change of package name ===
>  If the change from commons-foo:commons-foo to org.apache.commons:commons-foo is accompanied
by a change to the Java package name, e.g. to org.apache.commons.foo3, then there will be
no classpath issue, as both Maven and Java treat the artifacts as different.
> 
> - However, the change of Java package name is neither binary nor source-compatible, and
can require a lot of work for users of Commons Foo. This may be acceptable if the new version
has major changes to the API, but not otherwise - why should users (who may not even use Maven)
be forced to change their code just to upgrade to the latest version (James Carman: the user
will thank us when they try to use a library that requires the older version, we shouldn't
discount this too mcuh.  This approach solves the "jar hell" issue)?
> + There are two possible scenarios here
> + * The new version of the code is binary incompatible with the old version.
> + * The new version is binary compatible with the old version.
> 
> + However, the change of Java package name is neither binary nor source-compatible, and
can require a lot of work for users of Commons Foo. This may be acceptable if the new version
has incompatible changes to the API, but not otherwise - why should users (who may not even
use Maven) be forced to change their code just to upgrade to the latest version (James Carman:
the user will thank us when they try to use a library that requires the older version, we
shouldn't discount this too much.  This approach solves the "jar hell" issue) (Sebb: there
is no "jar hell" if the versions are binary compatible)?
> + 
> + For binary-compatible releases, the Java package name should NOT be changed, as that
causes unnecessary work for all users.
> + It follows that the Maven groupID should not be changed either, unless relocation POMs
are guaranteed to work.
> + 
> + As a concrete example, Logging uses the groupId commons-logging. Changing the package
name merely to allow the groupId to be changed would cause an awful lot of work, for almost
no benefit.
> + 
> 
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