What are Maven goals and phases and what is their difference?

Question

What is the difference/relation between Maven goals and phases? How they are related to each other?

Answer 1

The definitions are detailed at the Maven site's page Introduction to the Build Lifecycle, but I have tried to summarize:

Maven defines 4 items of a build process:

1. Lifecycle

   Three built-in lifecycles (aka build lifecycles): default, clean, site. (Lifecycle Reference)

2. Phase

   Each lifecycle is made up of phases, e.g. for the default lifecycle: compile, test, package, install, etc.

3. Plugin

   An artifact that provides one or more goals.

   Based on packaging type (jar, war, etc.) plugins' goals are bound to phases by default. (Built-in Lifecycle Bindings)

4. Goal

   The task (action) that is executed. A plugin can have one or more goals.

   One or more goals need to be specified when configuring a plugin in a POM. Additionally, in case a plugin does not have a default phase defined, the specified goal(s) can be bound to a phase.

Maven can be invoked with:

1. a phase (e.g clean, package)
2. : (e.g. dependency:copy-dependencies)
3. :[:]: (e.g. org.apache.maven.plugins:maven-compiler-plugin:3.7.0:compile)

with one or more combinations of any or all, e.g.:

mvn clean dependency:copy-dependencies package