Maven Modules + Building a Single Specific Module

Question

I have a multi-module Maven project with a parent project P and three sub-modules A, B, and C. Both B and C are war projects and both depend on A.

I can type mvn compile in P and have all of the sub-modules properly compiled. The problem comes when I want to do operations for specific modules.

I'd like to be able to package a war for project B, but when I run the package command from B's directory, it complains that it can't find the dependencies for A.

I understand from this question: Maven and dependent modules that perhaps Maven isn't really designed for this type of dependency resolution, but that begs the question of how do I package B?

1. Do I have to run mvn package for the entire project hierarchy when I really just want B?

2. Do I have to install snapshots of A into my local repository every time I want to package B?

This second scenario isn't much fun when A is still under active development.

Any best practices here?

Answer 1

Any best practices here?

Use the Maven advanced reactor options, more specifically:

-pl, --projects         Build specified reactor projects instead of all projects -am, --also-make         If project list is specified, also build projects required by the list 

So just cd into the parent P directory and run:

mvn install -pl B -am 

And this will build B and the modules required by B.

Note that you need to use a colon if you are referencing an artifactId which differs from the directory name:

mvn install -pl :B -am 

As described here:

• Define modules list which shall be build in Maven multiproject build

Answer 2

Say Parent pom.xml contains 6 modules and you want to run A, B and F.

<modules>         <module>A</module>         <module>B</module>         <module>C</module>         <module>D</module>         <module>E</module>         <module>F</module>   </modules> 

1- cd into parent project

 mvn --projects A,B,F --also-make clean install 

OR

mvn -pl A,B,F -am clean install 

OR

mvn -pl A,B,F -amd clean install 

Note: When you specify a project with the -am option, Maven will build all of the projects that the specified project depends upon (either directly or indirectly). Maven will examine the list of projects and walk down the dependency tree, finding all of the projects that it needs to build.

While the -am command makes all of the projects required by a particular project in a multi-module build, the -amd or --also-make-dependents option configures Maven to build a project and any project that depends on that project. When using --also-make-dependents, Maven will examine all of the projects in our reactor to find projects that depend on a particular project. It will automatically build those projects and nothing else.