1

I have a project with a parent aggregator module and 3 children modules. I don't know if this is a bug for me or just how Maven works, but I am currently unable to deploy one of my children modules without also deploying the respective parent. When I try to import the child module on another project of mine, Maven throws an error saying it can't resolve the parent. If I deploy both to my Nexus, it works perfectly. Do I always have to deploy both?

Tiago Silva
  • 455
  • 5
  • 20

2 Answers2

3

Yes.

You always need the parent POM as well.

J Fabian Meier
  • 33,516
  • 10
  • 64
  • 142
1

When Maven need to "use" a module, it needs to resolve it.
If this module has ancestors it needs to access to every ones to resolve it.

OR you will face somethings like :

Could not resolve dependencies for project org.projectB:childA-Consumer:jar:0.1.0:
Failed to collect dependencies at org.projectA:childA:jar:0.1.0: 
Failed to read artifact descriptor for org.projectA:childA:jar:0.1.0: 
Could not find artifact org.projectA:parent:pom:0.1.0

Solution 1 : Deploy the parent

The common way is to deploy the parent, so this way when you consume your module maven will be able to find ancestors and so resolve your module's pom.

But lot of users seems to consider this as not so satisfying. (There are many question about that on stackoverflow ...)

Solution 2 : Parent != Aggregator

Most of the time in multi-module project, the aggregator pom is also the parent pom but this is 2 different concepts.

  • parent : is about sharing configuration with inheritance.
  • aggregator : is about building several modules at same time.

(more details about aggregator vs parent differences)

So, you can have an aggregator with several children and each child has no parent.
This way you don't have to deploy your aggregator.

Drawback you can not use inheritance to share config between modules.
Note that this is not a drawback for everyones, some consider that using inheritance and so parent is not good idea.

Solution 3 : Use Maven Flatten Plugin

Currently poms contains 2 kind of information :

  • how to build the artifact,
  • how to consume it (e.g. dependencies).

Maven 5 will maybe clarify this and so you could have a different pom in your released artifacts and in your source code.

Using Maven 3, there is a plugin which aims to do that : flatten-maven-plugin
It aims to generate a pom.xml consumers oriented.
Among others, parent relationship is resolved, flattened and removed.

This way, you can use parents to share configuration between modules (with inheritance) and not deploy your aggregator and/or parents .

Drawback, you could maybe face issues with some other maven plug-in interaction ?

Some tips you need to know if you wan to use flatten-maven-plugin :

sbernard
  • 444
  • 3
  • 16