Hi again everyone.
I have taken some time and installed a nexus locally, and I have been
playing with different alternatives for how to solve my problem....
To recap, I have JDOM versions 1.x and 2.x both currently deployed in
the artifact 'jdom' even though these versions internally have different
packages (org.jdom.* and org.jdom2.* ). The problem is that it is
necessary in some conditions to have both version 1.x and 2.x in a maven
project (typically because the 1.x version is used by some third-party
dependency).
I have been trying to find the 'best' way to 'recover' the mess in the
JDOM artifact so that it is possible to have both 1.x as well as 2.x,
but to do it in such a way that it has the least impact on current
users, and for those users who *need* both versions, it can be done as
simply as possible.
In my experimentation I think I have found that the *easiest* and also
the *neatest* solution is to duplicate the latest JDOM 1.x artifact with
a different artifact-id. In my local nexus I have duplicated the JDOM
1.1.3 artifact as jdom.dep 1.1.3.
The way I see this working is that for the 'simple' user, they do not
have the complicated requirement to have both 1.x and 2.x. In their case
they can just continue doing what they do.... and when they are ready
they can upgrade their code to use JDOM 2.x, changing their dependency
from jdom 1.x to jdom 2.x when they do.
For the complicated user, they will be needing both versions. Right now
they can't run their code because they can't have both 1.x and 2.x in
their compile. In the typical case there is a third-party dependency
which in turn depends on jdom 1.x. Since 'our' project depends on jdom
2.x and the 3rd party depends on 1.x, maven will automatically just pull
the 'newer' jdom 2.x version. This means that the 3rd-party code will be
failing because it is missing classes.
In this case, we can simply add the 'jdom.dep' artifact to our project,
specifying the 1.x version.
I have 'worked through' the various scenarios, and I think it can be
expressed as follows:
Say I have my project. It has the simple dependency:
<dependency>
<groupId>org.jdom</groupId>
<artifactId>jdom</artifactId>
<version>2.0.1</version>
<scope>compile</scope>
</dependency>
Now I want to include the additional dependency (this is just some
'arbitrary' dependency which has an internal dependency to jdom 1.1):
<dependency>
<groupId>net.sourceforge.htmlcleaner</groupId>
<artifactId>htmlcleaner</artifactId>
<version>2.2</version>
</dependency>
Unfortunately this htmlcleaner code will not work because I am missing
the org.jdom.* classes because maven has only used the jdom 2.0.1
version which only has the org.jdom2.* classes.
The solution is, in my project, to also include the 'duplicate' 1.x
dependency:
<dependency>
<groupId>org.jdom</groupId>
<artifactId>jdom.dep</artifactId>
<version>1.1.3</version>
</dependency>
The bottom line is that only those people who require both versions will
be affected, and the solution only requires adding a new dependency to
the project, and there is no need to do 'exclusions' or other 'shady'
logic....
Further, there is no need for the 'normal' JDOM user (they only require
the one version of JDOM) to worry about anything because things just
stay the same.... there is nothing to change.
I would greatly appreciate it if this 'plan' could be inspected and
criticized/poked/verified/etc.
Thanks in advance
Rolf
On 29/05/2012 11:38 AM, Rolf Lear wrote:
On Tue, 29 May 2012 16:22:27 +0100, Stephen Connolly
<stephen.alan.conno...@gmail.com> wrote:
On 29 May 2012 15:26, Rolf Lear<j...@tuis.net> wrote:
So, being inexperienced, my intention is to find some solution that:
1. makes it possible (even if playing exclusion games is needed) to use
both JDOM 1.x and 2.x in a maven project (currently it is not).
Well actually it is possible to work around the issue if you are
prepared to introduce a wrapper project...
something like this:
Hmmm... this has gone over my head.... I think I am going to have to spend
some time getting to grips with some of the more details in maven...
Perhaps I should take a few days and set up my own repo, and try these
things out...
For what it's worth, I am not sure the maven-shade-plugin is
appropriate.... is it? I am not sure how that usage of it helps... I simply
don't know enough.
Bottom line is that I don't know enough yet... must learn more.
Thanks all, I'll figure some more things out and come back with 'more of a
clue'.
Rolf
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