This document describes some of the most common terms encountered while using Maven. These terms, that have an explicit meaning for Maven, can sometimes be confusing for newcomers.
| Term | Description |
|---|---|
| Project | Maven thinks in terms of projects. Everything that you will build are projects. Those projects follow a well defined "Project Object Model". Projects can depend on other projects, in which case the latter are called "dependencies". A project may consistent of several subprojects, however these subprojects are still treated equally as projects. |
| Project Object Model (POM) |
The Project Object Model, almost always referred as the POM for brevity,
is the metadata that Maven needs to work with your project. Its name is
"project.xml" and it is located in the root directory of each project.
To learn how to build the POM for your project, please read about the project descriptor. |
| Artifact | An artifact is something that is either produced or used by a project. Examples of artifacts produced by Maven for a project include: JARs, source and binary distributions, WARs. Each artifact is uniquely identified by a group ID and an artifact ID which is unique within a group. |
| Group ID |
A group ID is a universally unique identifier for a project. While this is often just
the project name (eg. commons-collections), it is helpful to use a fully-qualified
package name to distinguish it from other projects with a similar name (eg. org.apache.maven).
|
| Dependency | A typical Java project relies on libraries to build and/or run. Those are called "dependencies" inside Maven. Those dependencies are usually other projects' JAR artifacts, but are referenced by the POM that describes them. |
| Plugin | Maven is organized in plugins. Every piece of functionality in Maven is provided by a plugin. Plugins provide goals and use the metadata found in the POM to perform their task. Examples of plugins are: jar, eclipse, war. Plugins are written in Jelly and can be added, removed and edited at runtime. |
| Goal |
Goals are what are executed to perform an action on the project. For example, the
jar:jar will compile the current project and produce a JAR.
Each goal exists in a plugin (except for those that you define yourself), and the
goal name usually reflects the plugin (eg. java:compile comes from the
java plugin).
|
| Repository |
A repository is a structured storage of project artifacts. Those
artifacts are organized under the following structure:
$MAVEN_REPO/groupId/artifact type/project-version.extension
For instance, a Maven JAR artifact will be stored in a repository under /repository/maven/jars/maven-1.0-beta-8.jar.
There are different repositories that Maven uses. The "remote repositories" are a list of repositories to download from. This might include an internet repository, its mirrors, and a private company repository. The "central repository" is the one to upload generated artifacts to (for developers of a company for instance). The "local repository" is the one that you will have on your computer. Artifacts are downloaded just once (unless they are a SNAPSHOT) from the remote repository to your local repository. |
| Snapshots |
Projects can (and should) have a special version including SNAPSHOT
to indicate that they are a "work in progress", and are not yet released. When a
snapshot dependency is encountered, it is always looked for in all remote repositories,
and downloaded again if newer than the local copy.
The version can either be the string SNAPSHOT itself, indicating
"the very latest" development version, or something like 1.1-SNAPSHOT,
indicating development that will be released as 1.1 (i.e. newer than 1.0, but not yet 1.1).
|
| XDoc |
XDoc is the format of documentation that Maven currently understands. It is quite simple, and
allows embedding XHTML within a simple layout that is transformed into a uniform site.
For information on how to create XDoc files, refer to the Building a Project Web Site document. |
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