maven – mvn clean install – lifecycle, phase, goals

If someone is using maven , it is very common to hear , “Please execute mvn clean install”. But is it a correct way to convey the actual meaning ? Are clean and install strictly some parameters to mvn command. If yes, then what does those parameters mean ?

In today’s article I am going to explain what does mvn clean install actually means and what does it really means to maven.
maven – lifecycle, phase, goals

For any project the build process is very important and this is where maven brings the discipline; by clearly defining the  build lifecycle. It defines what it should be composed of and when it should be executed.

In maven, at the highest level there is lifecycle, each lifecycle has phases and each phases is composed of goals.

    Lifecycle : There are three pre-defined build lifecycle in maven : default, clean and site.
    Phases :   Every build lifecycle comprises of phases

For example:

    The clean lifecycle has following phases :
        pre-clean
        clean
        post-clean
    The default lifecycle has the following phases :
        validate
        compile
        test
        package
        integration-test
        verify
        install
        deploy

    Goals : The build phases itself carries out its tasks with the help of defined goals and goals attached to it. The goals represent a specific tasks. For a build phase to be executed, one or more goals need to be defined.  An example of goal is compiler:compile which is executed with compile phase if default build lifecycle.

In a nutshell, a particular lifecycle has phases and phases have goals.

With number of goals defined, does maven executes all the goals or few ? If few, how does it decides ?

For this it looks up the packaging element defined in pom.xml file. Commonly used values are jar,ear and war.  Based on the packaging element defined, maven selects goals and binds them to build phases. So for packaging jar, following goals are bound to build phases :

build phase


Goal

process-resources


resources:resources

compile


compiler:compile

process-test-resources


resources:testResources

test-compile


compiler:testCompile

test


surefire:test

package


jar:jar

install


install:install

deploy


deploy:deploy

So when we say “mvn clean install”, what we are actually saying is :

Execute the clean build lifecycle (this will execute all the phases of clean lifecycle), followed by install phase if default lifecycle.

Maven will in-turn use the packaging element to decide the goals to be executed for the given phase.