We would like to create a partial archetype to add a custom-pom.xml as well as other resources into an existing project. The custom pom will then be used in the generated project via mvn -f custom-pom.xml.
Our archetype therefore contains a src/main/resources/archetype-resources/osgi-pom.xml, but does not contain a pom.xml in the same directory.
We used archetype:generate parameterised appropriately to run this archetype on an existing project. This produces:
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-archetype-plugin:2.2:generate (default-cli) on project standalone-pom: org.apache.maven.archetype.exception.ArchetypeGenerationFailure: Error merging velocity templates: Unable to find resource 'archetype-resources/pom.xml' -> [Help 1]
As a test, we created a dummy archetype-resources/pom.xml then re-ran the generate goal. This produces:
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-archetype-plugin:2.2:generate (default-cli) on project standalone-pom: Don't override file /tmp/archetype/fabric-rf-server/pom.xml -> [Help 1]
We saw this example which has no archetype-resources/pom.xml. We are using the Archetype 2.0x standard however, which is possibly why the tactic works for that author but not ourselves.
How can we resolve this problem? Is a partial archetype unsuitable for inserting resources into an existing Maven project - must the project instead be non-Maven?
We've scoured the Maven Archetype plugin 2.2 documentation but there's barely any mention of partial archetypes and their specialised behaviour.
It turns out the second error message listed in OP is because of conflicting POM properties (the artifactId, groupId and version). Removing these from the archetype-resources/pom.xml solved the issue.
What actually happens with a partial archetype is the existing project has its POM merged with that in the archetype. So this property conflict was causing the merge to fail.
We identified that a merge should occur after exploring the source code.