jdeps does not add jdk.random when using RandomGenerator.getDefault()

Question

I have a Java 17 application which uses RandomGenerator.getDefault() in it. When I use jdeps to create a minified JRE for it, it does not add jdk.random, so the JRE created by jlink cannot run the application. Is there something I missed?

Answer 1

The RandomGenerator interface is in the module java.base, which can not depend on any other module, including jdk.random.

Instead it uses the ServiceLoader API to find implementations of RandomGenerator. The jdk.random module provides several implementations of the RandomGenerator interface:

> java --describe-module jdk.random
jdk.random@19
...
provides java.util.random.RandomGenerator with jdk.random.L32X64MixRandom jdk.random.L64X128MixRandom jdk.random.L64X128StarStarRandom jdk.random.L64X256MixRandom jdk.random.L64X1024MixRandom jdk.random.L128X128MixRandom jdk.random.L128X256MixRandom jdk.random.L128X1024MixRandom jdk.random.Xoroshiro128PlusPlus jdk.random.Xoshiro256PlusPlus
...

However, since there is no explicit dependency from java.base to jdk.random, it is not included automatically when you include java.base.

Modules that implement services have to be included manually using --add-modules when running jlink instead.

You can use jlink's --suggest-providers option to get a list of modules that implement a service:

> jlink --suggest-providers java.util.random.RandomGenerator

Suggested providers:
  java.base provides java.util.random.RandomGenerator used by java.base
  jdk.random provides java.util.random.RandomGenerator used by java.base

(There's also the --bind-services flag, but that will include ALL service implementations, which is probably not what you want)