Post#88.Maven Commands

Maven Commands

Maven contains a wide set of commands which you can execute. Maven commands are a mix of build life cycles, build phases and build goals, and can thus be a bit confusing. Therefore I will describe the common Maven commands in this tutorial, as well as explain which build life cycles, build phases and build goals they are executing.

Maven Command Structure

A Maven command consists of two elements:

1.      mvn

2.      One or more build life cycles, build phases or build goals

Here is a Maven command example:

mvn clean

This command consists of the mvn command which executes Maven, and the build life cycle named clean.

Here is another Maven command example:

mvn clean install

This maven command executes the clean build life cycle and the install build phase in the default build life cycle.

You might wonder how you see the difference between a build life cycle, build phase and build goal. I will get back to that later.

Build Life Cycles, Phases and Goals

Maven contains three major build life cycles:

• clean
• default
• site

Inside each build life cycle there are build phases, and inside each build phase there are build goals.

You can execute either a build life cycle, build phase or build goal. When executing a build life cycle you execute all build phases (and thus build goals) inside that build life cycle.

When executing a build phase you execute all build goals within that build phase. 

Buid goals are assigned to one or more buid phases. When the build phases are executed, so are all the goals in that build phase. You can also execute a build goal directly.

Executing Build Life Cycles, Phases and Goals

When you run the mvn command you pass one or more arguments to it. These arguments specify either a build life cycle, build phase or build goal. For instance to execute the clean build life cycle you execute this command:

mvn clean

To execute the site build life cycle you execute this command:

mvn site

Executing the Default Life Cycle

The default life cycle is the build life cycle which generates, compiles, packages etc. your source code.

You cannot execute the default build life cycle directly, as is possible with the clean and site. Instead you have to execute a specific build phase within the default build life cycle.

The most commonly used build phases in the default build life cycle are:

Build Phase	Description
validate	Validates that the project is correct and all necessary information is available. This also makes sure the dependencies are downloaded.
compile	Compiles the source code of the project.
test	Runs the tests against the compiled source code using a suitable unit testing framework. These tests should not require the code be packaged or deployed.
package	Packs the compiled code in its distributable format, such as a JAR.
install	Install the package into the local repository, for use as a dependency in other projects locally.
deploy	Copies the final package to the remote repository for sharing with other developers and projects.

Executing one of these build phases is done by simply adding the build phase after the mvn command, like this:

mvn compile

This example Maven command executes the compile build phase of the default build life cycle. This Maven command also executes all earlier build phases in the default build life cycle, meaning the validate build phase.

Executing Build Phases

You can execute a build phase located inside a build life cycle by passing the name of the build phase to the Maven command. Here are a few build phase command examples:

mvn pre-clean

mvn compile

mvn package

Maven will find out what build life cycle the specified build phase belongs to, so you don't need to explicitly specify which build life cycle the build phase belongs to.