Duplicate artifactId in child pom

Question

I want a parent pom to define some properties for numerous child poms to inherit. However when I try and use the artifactId within one of these properties in the parent pom, it duplicates in the child's effective pom. Very basic example below. Assume I have all the valid fields needed for poms (groupId, version, packaging etc).

The parent pom's effective pom has a scm connection value of www.mysite.com/parent-pom. But the child's effective pom has a scm connection value of www.mysite.com/child-pom/child-pom. How do I gain this inheritance of the property and general structure of the connection url, without the duplicate artifactId. I want the child pom to have a scm connection of www.mysite.com/child-pom.

Parent:

<project>
  <artifactId>parent-pom</artifactId>
  <properties>
    <scmurl>www.mysite.com</scmurl>
  </properties>
  <scm>
    <connection>${scmurl}/${artifactId}</connection>
  </scm>
</project>

Child:

<project>
  <parent>
    <artifactId>parent-pom</artifactId>
  </parent>
  <artifactId>child-pom</artifactId>
</project>

The scm connections is one of the things which do not make sense to define properties for, cause at the first time you will do a release the properties will be replaced by the values and afterwards you have the literal values there which does not help in the end. Furthermore Are we talking about a multi module build? If yes than only the parent should have an scm element not the childs. — khmarbaise
Not talking about multi-module. I'm talking about separate projects. One parent which defines versions for common dependencies, and then any number of other projects would inherit this. One thing I wanted to define was the SCM url. — edwardmlyte
Try changing ${artifactId} to ${project.artifactId}. Does it help? — Eldad Assis
For independent project is does not make sense as well. So defining properties in your pom which inherits from a company pom only works for the first time you create the new project after the first release all those properties will be replaced by their values. — khmarbaise

333kenshin 333kenshin · Accepted Answer · 2014-11-05T08:57:27

edwardmlyte,

There are 2 solutions to what you're trying to do, but neither of them are optimal.

Fundamental Problem

If Maven SCM plugin detects that <scm> block has been defined in your parent but NOT in your child, then it will reason that your child's SCM path is simply the subdir of the parent. In your case there's an additional wrinkle that your parent's url itself contains ${project.artifactId} which gets interpolated at the child level prior to tacking on the artifactId again.

Basically, it's doing the following:

project.scm.connection=${parent.scm.connection}/${project.artifactId}
project.scm.connection=${scmurl}/${project.artifactId}/${project.artifactId}
project.scm.connection=www.mysite.com/child-pom/child-pom

The fact that your parent's url contains ${artifactId} compounds the confusion, but even if you hardcode the url to www.mysite.com/parent-pom/ you won't be able to get around the fact that SCM plugin thinks child-pom is a subdir of the parent's url and so will simply tack it onto the end of the path.

Your 2 options are:

Redundant but Simple

Put the following into every child's pom.xml file:

<scm>
    <connection>${scmurl}/${artifactId}</connection>
</scm>

It's annoying but relatively straightforward.

Efficient but Dodgy

Have parent-pom contain the following:

<scm>
    <connection>${scmurl}/</connection>
</scm>

That will result in each child will have correct url, but the parent itself will be messed up.

You can get around that problem by putting the parent's correct url into a profile:

<profile>
    <id>parent-profile</id>
    <scm>
        <connection>${scmurl}/parent-pom</connection>
    </scm>
</profile>


$ mvn -Pparent-profile ...

It's less obvious and prone to manual error, but it'll avoid the need to edit each child's pom file.

Hope that helps.

Duplicate artifactId in child pom

3 Answers