What is the difference between inheritance and submodule concepts in maven?

Question

What is the difference between inheritance and submodule concepts in maven? Lets say I have a project A whose parent is project B ? In that case is A a submodule of B or is it something entirely different ?

Answer 1

Inheritance concept in maven is very similar to inheritance in OOP. Usually you inherit (include <parent> section in your pom.xml) when you want to reuse other project's settings, like dependencies, repositories, build plugins etc.

Submodules concept is different. It addresses a very common case in software development when your project consists of some number of smaller projects, each serving its own goal. In maven terms it is accomplished through <modules> section in pom.xml. When you execute maven goal being in the root of the main project, this goal gets propagated to all of the subprojects and executed there as well.

In most of the cases, though, both of these concepts are utilized together. You have main pom.xml file that defines common dependencies, build lifecycle, settings, properties, repositories etc. and set of modules. Each of modules inherits configuration from the main pom.xml and might add something specific.