Maven Lifecycle and Goals

The previous section covered plugin goals and how to run goals from command line. In very few situations we invoke plugin goals directly and more often than not, lifecycle phases are preferred. In this chapter, we describe the link between Maven Lifecycle and
Goals.

Lifecycle Phases and Plugin Goals

When a lifecycle phase is run, depending on project type and packaging type, Maven binds plugin goals to lifecycle phases.

When we run 

mvn
package

 in a Java Project, Maven binds plugin goals to lifecycle phases as shown in the next figure.



To process-resources phase, Maven binds resources goal of maven-resources-plugin and to test phase, it binds test goal of maven-surefire-plugin and so on.

What’s happens at package phase is bit interesting. In a Java Project, Maven binds jar goal of maven-jar-plugin. However, when we run the same command in a webapp project, up to test phase Maven binds same goals, but to the package phase Maven binds war goal
of maven-war-plugin the war:war instead of jar:jar.

The command 

mvn
help:describe -Dcmd=<phase>

 is a very useful command not only to list the lifecycle phases but also to know the binded goal and plugin version. Run the following command from the project directory that contains the pom.xml.

$ mvn help:describe -Dcmd=clean

[INFO] ‘clean’ is a lifecycle with the following phases: 

* pre-clean: Not defined

* clean: org.apache.maven.plugins:maven-clean-plugin:2.5:clean

* post-clean: Not defined

We pass lifecycle phase 

clean

 with
argument 

-Dcmd

.
The help:describe validates the pom.xml and based
on project type outputs the sequence of lifecycle phases that will be executed for the lifecycle and plugin goals bounded to each phase. As we can see in the screenshot, no goals are bounded to pre-clean and post-clean phases
and they are indicated as not defined and for clean phase, clean:clean goal
of maven-clean-plugin (version 2.5) is attached.

The following command outputs the sequence of phases and goals for default lifecycle The phase deploy belongs to default lifecycle so command output details of default lifecycle.

$ mvn help:describe -Dcmd=deploy

It is a part of the lifecycle for the POM packaging ‘jar’.

This lifecycle includes the following phases:

* validate: Not defined

* initialize: Not defined

* generate-sources: Not defined

* process-sources: Not defined

* generate-resources: Not defined

* process-resources: org.apache.maven.plugins:maven-resources-plugin:2.6:resources

* compile: org.apache.maven.plugins:maven-compiler-plugin:3.1:compile

* process-classes: Not defined

* generate-test-sources: Not defined

* process-test-sources: Not defined

* generate-test-resources: Not defined

* process-test-resources: org.apache.maven.plugins:maven-resources-plugin:2.6:testResources

* test-compile: org.apache.maven.plugins:maven-compiler-plugin:3.1:testCompile

* process-test-classes: Not defined

* test: org.apache.maven.plugins:maven-surefire-plugin:2.12.4:test

* prepare-package: Not defined

* package: org.apache.maven.plugins:maven-jar-plugin:2.4:jar

* pre-integration-test: Not defined

* integration-test: Not defined

* post-integration-test: Not defined

* verify: Not defined

* install: org.apache.maven.plugins:maven-install-plugin:2.4:install

* deploy: org.apache.maven.plugins:maven-deploy-plugin:2.7:deploy

Lifecycles, Lifecycle Phases, Plugins and Plugin Goals are the core of Maven. and we summarize the concepts learned so far:

Maven comes with three lifecycles – default, clean and site.

each lifecycle is made up of lifecycle phases and in all, there are 28 phases – default 21, clean 3 and site 4.

when a lifecycle phase is invoked using mvn command, all preceding phases are executed sequentially one after another.

lifecycle phases by themselves doesn’t have any capabilities to accomplish some task and they rely on plugins to carryout the task.

depending on project and packaging type, Maven binds various plugin goals to lifecycle phases and goals carryout the task entrusted to them.