Multi-Module Maven Projects: Difference between revisions

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For considerations on the version, see "[[#Modules_and_Versions|Modules and Versions]]" section.
For considerations on the version, see "[[#Modules_and_Versions|Modules and Versions]]" section.


Each <tt><module></tt> element corresponds to a ''subdirectory'' of the top level project directory. Maven will look into these subdirectories for <tt>pom.xml</tt> files. Each module will have its own independent source hierarchy.
Each <tt><module></tt> element corresponds to a ''subdirectory'' of the top level project directory. Maven will look into these subdirectories for <tt>pom.xml</tt> files, and it will add the modules to the list of Maven projects included in a build. Each module will have its own independent source hierarchy.


=Organizatorium=
=Organizatorium=


* The modules do not need to specify their <tt><groupId></tt>, as it is inherited from their parent, and thus redundant.
* The modules do not need to specify their <tt><groupId></tt>, as it is inherited from their parent, and thus redundant.

Revision as of 17:45, 4 November 2016

External

Internal

Overview

For guidelines on when it is appropriate to use modules, and when separate projects, see "When We Should Use Modules ?" section.

The Reactor

When We Should Use Modules?

Two major benefits of a multi-module project are that all the parts can be built with a single command, and Maven handles the correct build order.

Modules and Versions

Different modules of the same project can have different versions.

In case all modules evolve keeping maintaining their versions in lockstep, that version is specified in the parent POM.

if the version of the modules evolve independently, this can be made clear by specifying the parent POM version to be 0.

POM Structure

The Parent POM

A multi-module project is defined by a parent POM referencing one or more submodules. The essential elements are the packaging, which is of type "pom", and the list of modules.

<project>
    ...
    <groupId>...</groupId>
    <artifactId>...</artifactId>
    <version>...</version>

    <packaging>pom</packaging>

    ...
    <modules>
        <module>module1</module>
        <module>module2</module>
    </modules>
    ...
</project>

The "pom" packaging indicates that the single purpose of this (top-level) project is to provide a container Project Object Model.

The group ID will be shared with the modules.

The artifact ID does not really matter. We conventionally use the "maven-root" value.

For considerations on the version, see "Modules and Versions" section.

Each <module> element corresponds to a subdirectory of the top level project directory. Maven will look into these subdirectories for pom.xml files, and it will add the modules to the list of Maven projects included in a build. Each module will have its own independent source hierarchy.

Organizatorium

  • The modules do not need to specify their <groupId>, as it is inherited from their parent, and thus redundant.