ok so how does maven work…

There’s a plugin architecture. This seems weird at first (“you need a plugin to compile java? i thought maven was the java build tool”) but I think it does make sense with the model

build lifecycle

there are three builtin lifecycles - default, clean, site

each lifecycle consists of a number of phases https://maven.apache.org/guides/introduction/introduction-to-the-lifecycle.html#Lifecycle_Reference . when you execute a phase, you also execute all the phases before it.

for example the initialize phase is responsible for creating the target directory. this must happen before the compile phase, which populates that directory, and the test phase, which requires the project be compiled first. so when you run mvn test it will first initialize, then compile, then test.

another simpler example is, say, the site lifecycle. first you prepare to generate the site, then you generate the site, then you deploy the site.

ANNOYING: there is no way to hook more phases onto an existing build lifecycle. maybe the reduced complexity cost is worth it

goals

what does it mean to “run a phase”? when maven “runs the test phase” what does it actually do?

the answer is that phases have a list of goals bound to them. running a phase means executing all of the goals.

there are a handful of ways to assign goals to phases:

• explicitly, in a <phases> block in your pom
• by adding a plugin - plugins can bind their own goals to a phase (?)
  • or maybe the <executions> tag is relevant here
• by setting a <packaging> type, which sets up a predefined set of goals from a handful of plugins https://maven.apache.org/ref/3.9.8/maven-core/default-bindings.html
  • all projects that don’t otherwise set a packaging type default to jar. which is why maven can build simple java proejcts with little other configuration.

the command line

typical maven invocation: mvn clean package

• first runs clean from the clean lifecycle
• then runs package from the default lifecycle

you can also mix in goals (which have the form plugin-id:goal-name i think). uhhh.

the pom

The pom: https://maven.apache.org/guides/introduction/introduction-to-the-pom.html

required things are modelVersion (which is 4.0.0, other values are reserved for furuter expansion/back-compat), and the famous “maven coordinates”, groupId artifactId and version.