jdeps on a directory

Question

How does jdeps works when using it on a directory?

I'm basically working with a tomcat webapp that has a complex structure, with many jars and classes at several locations and I want to generate a lightweight JRE with jlink.

The directory is a classic tomcat structure, which contains jars and classes at several locations :

> tree -L 1 /usr/local/tomcat/                                                                                                                  
├── LICENSE
├── NOTICE
├── RELEASE-NOTES
├── bin
├── conf
├── db.sh
├── favicon.ico
├── lib
├── logs
├── run
├── save.sh
├── start.sh
├── stop.sh
├── temp
├── webapps
└── work

> find . -name "*.jar" -o -name "*.class" | wc -l                                                                                             
     938

I've been trying to use jdeps in several ways but the docs are not super helpfull. Below is the only command that returned something looking like what I'd expect:

> jdeps --recursive --print-module-deps /usr/local/tomcat/
java.base,java.compiler,java.desktop,java.management,java.naming,java.scripting,java.sql

That kind of works as expected, but it seems to only take the classes into account. Without --print-module-deps I get a whole bunch of unknown dependencies like this

com.my.app -> org.eclipse.jgit.diff  not found

Even though the dependecy is properly installed at /usr/local/tomcat/webapps/ROOT/WEB-INF/lib/org.eclipse.jgit-5.10.0.202012080955-r.jar.

As an obvious consequence, there are a lot of unlisted needed modules, and when executing the app with the custom JRE, I get errors because of the missing java modules. To clarify, if I include all modules with jlink --add-modules ALL-MODULE-PATH everything runs smoothly.

Edit

I've tested runnning jdeps on every single jar to add the missing modules, even though a more direct / efficient approach with jdeps would be better.

The find . -name "*.jar" -o -name "*.class" | xargs jdeps --print-module-deps --ignore-missing-deps seems to do the trick on this basic usecase, but when applied to the bigger tomcat project, there still are runtime exceptions so I think the ignore-missing-deps makes it pointless.