List modules in jar file

Question

I've created what I'm pretty sure is a modular jar file. But if possible, I'd like to double check. Given a jar file, is there a way to determine what modules the compiler would find within it?

Carney

Answer 1

The alternative is to use the jar --describe-module (-d for short), e.g.:

jar --file=myjar.jar --describe-module

Chaudfroid

Answer 2

You can list the modules within the jar using the following java tool command:-

java -p yourModular.jar --list-modules

Edit: You shall preferably make use of the jar command lin as suggested in @Alan's answer.

Dilapidate

I recommend to use jar --describe-module instead - it's much more precise and contains more relevant information. – Lane

This way is handy for checking which modules are built into the runtime image (say as built using jlink/jpackage) with java --list-modules. – Greataunt

Answer 3

To extract the contents of a JAR file to see what’s inside, change the extension of the JAR from .jar to .zip. Then you can extract the files with whatever zip extraction tool you choose.

Barrada

I know how to extract the jar. I was wondering if there was an easier way to determine what modules it contains than poring over the source files. – Carney

Modules? Do you mean external libraries? – Barrada

No, modules as in Java 9 modules, aka project Jigsaw… – Carney

I’m sorry, I’ve never worked in Java 9. I misunderstood the question. I don’t know if any way to do what you are asking. – Barrada