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Maven: The Definitive Guide

Cover of Maven: The Definitive Guide by Sonatype Company Published by O'Reilly Media, Inc.

Project Relationships

One of the compelling reasons to use Maven is that it makes the process of tracking down dependencies (and dependencies of dependencies) very easy. When a project depends on an artifact of another project, we can say that this artifact is a dependency. In the case of a Java project, this can be as simple as a project depending on an external dependency such as Log4J or JUnit. Although dependencies can model external dependencies, they can also manage the dependencies between a set of related projects; if project-a depends on project-b, Maven is smart enough to know that project-b must be built before project-a.

Relationships are not only about dependencies and figuring out what one project needs to be able to build an artifact. Maven can model the relationship of a project to a parent, and the relationship of a project to submodules. This section gives an overview of the various relationships between projects and how such relationships are configured.

More on Coordinates

Coordinates define a unique location for a project. They were first introduced in Chapter 3. Projects are related to one another using Maven coordinates. project-a doesn’t just depend on project-b; a project with a groupId, artifactId, and version depends on another project with a groupId, artifactId, and version. To review, a Maven coordinate is made up of three components:


A groupId groups a set of related artifacts. Group identifiers generally resemble a Java package name. For example, ...

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