Coordinates & Packaging

## What are Maven coordinates? Maven is a build tool that stores every built artifact (a JAR, WAR, etc.) in a **repository** — a structured directory tree (your local `~/.m2/repository`, plus remote ones like Maven Central). To find any artifact unambiguously, Maven gives each one an address called its **coordinates**, commonly abbreviated **GAV**. ## The three core coordinates - **groupId** — a namespace identifying the organization or team that owns the artifact. By convention it uses reverse-DNS, e.g. `org.apache.commons`. This avoids name clashes between different vendors. - **artifactId** — the name of the specific project/module within that group, e.g. `commons-lang3`. Must be unique within the group. - **version** — the release identity, e.g. `3.14.0`. Distinguishes builds of the same project over time. ## How coordinates map to a path Maven turns GAV into a repository path by replacing dots in groupId with slashes: ``` org/apache/commons/commons-lang3/3.14.0/commons-lang3-3.14.0.jar ``` The filename is `<artifactId>-<version>[-<classifier>].<extension>`. ## Two optional coordinates - **packaging** (`<packaging>`) — defaults to `jar`. It selects the build lifecycle bindings and the output type (jar, war, pom, etc.). - **classifier** (`<classifier>`) — an optional suffix that lets one GAV ship multiple artifacts, e.g. `sources`, `javadoc`, or a platform-specific build. ## In a pom.xml ```xml <project> <modelVersion>4.0.0</modelVersion> <groupId>com.example</groupId> <artifactId>billing-service</artifactId> <version>1.4.2</version> <packaging>jar</packaging> </project> ``` The same triple appears when you depend on something: ```xml <dependency> <groupId>org.apache.commons</groupId> <artifactId>commons-lang3</artifactId> <version>3.14.0</version> </dependency> ``` Maven uses GAV both to publish your project's output and to resolve every dependency (and their transitive dependencies) from repositories.