How to include a maven module outside of the project context?

Question

I'd like to have a module in some kind of global project directory, so that I can include that module in all other projects that use that common code.

But how can I then tell a maven parent pom to include and compile this global shared module? The following does not work:

svn/MyGlobalProject/project-commons/pom.xml           //should be shared among different projects
svn/MyProject/web-parent/trunk/pom.xml                //the parent pom used to build the application
svn/MyProject/web-parent/trunk/project-domain/pom.xml //submodule 1
svn/MyProject/web-parent/trunk/project-web/pom.xml    //submodule 2

parent pom.xml:

<project>
        <groupId>de.project</groupId>
    <artifactId>project-parent</artifactId>
    <packaging>pom</packaging>

    <modules>
        <module>project-domain</module>
        <module>project-web</module>
        <module>../project-commons</module> <!-- Error -->
    </modules>
</project>

mvn package results in:

Child module trunk\project-commons of trunk\pom.xml does not exist

Answer 1

If you run mvn install on that global project, it will be installed in your local repository. Your other projects can then reference it as a dependency:

<dependency>
  <groupId>whatever</groupId>
  <artifactId>project-commons</artifactId>
  <version>1.0</version>
</dependency>

The downside of this simplistic approach is that your other projects won't compile until you've checked-out project-commons and run mvn install.

A more advanced approach is to deploy a network-accessible repository (such as Artifactory or Nexus) which you can deploy global artifacts to. Artifactory has a community edition which is free. You can then list this repository in your settings file and Maven will resolve artifacts that are uploaded to it.