How to list active sub-modules in a Maven project?

Question

I have a complex project where there are many directories that have POM files, but only some of which are sub-modules (possibly transitively) of a particular parent project.

Obviously, Maven knows the list of relevant files because it parses all the <module> tags to find them. But, I only see a list of the <name>s in the [INFO] comments, not the paths to those modules.

Is there a way to have Maven output a list of all the POM files that provided references to projects that are part of the reactor build for a given project?

Answer 1

Here's a way to do this on Linux outside of Maven, by using strace.

$ strace -o opens.txt -f -e open mvn dependency:tree > /dev/null
$ perl -lne 'print $1 if /"(.*pom\.xml)"/' opens.txt 

The first line runs mvn dependency:tree under strace, asking strace to output to the file opens.txt all the calls to the open(2) system call, following any forks (because Java is threaded). This file looks something like:

9690  open("/etc/ld.so.cache", O_RDONLY) = 3
9690  open("/lib/libncurses.so.5", O_RDONLY) = 3
9690  open("/lib/libdl.so.2", O_RDONLY) = 3

The second line asks Perl to print any text inside quotes that happens to end in pom.xml. (The -l flag handles printing newlines, the -n wraps the code single quotes in a loop that simply reads any files on the command line, and the -e handles the script itself which uses a regex to find interesting calls to open.)

It'd be nice to have a maven-native way of doing this :-)

Answer 2

I don't have a direct answer to the question. But using some kind of "module path" as naming convention for the <name> of my modules works for me. As you'll see, this convention is self explaining.

Given the following project structure:

.
├── pom
│   ├── pom.xml
│   └── release.properties
├── pom.xml
├── samples
│   ├── ejb-cargo-sample
│   │   ├── functests
│   │   │   ├── pom.xml
│   │   │   └── src
│   │   ├── pom.xml
│   │   └── services
│   │       ├── pom.xml
│   │       └── src
│   └── pom.xml
└── tools
    ├── pom.xml
    └── verification-resources
        ├── pom.xml
        └── src

Here is the output of a reactor build:

$ mvn compile
[INFO] Scanning for projects...
[INFO] Reactor build order: 
[INFO]   Personal Sandbox - Samples - Parent POM
[INFO]   Personal Sandbox - Samples - EJB3 and Cargo Sample
[INFO]   Personal Sandbox - Tools - Parent POM
[INFO]   Personal Sandbox - Tools - Shared Verification Resources
[INFO]   Personal Sandbox - Samples - EJB3 and Cargo Sample - Services
[INFO]   Personal Sandbox - Samples - EJB3 and Cargo Sample - Functests
[INFO]   Sandbox Externals POM
...

This gives IMHO a very decent overview of what is happening, scales correctly, and it's pretty easy to find any module in the file system in case of problems.

Not sure this does answer all your needs though.