On Fri, 26 Apr 2024 13:45:39 GMT, Alan Bateman <al...@openjdk.org> wrote:
> How useful is it to deploy with additional RandomGenerator implementations on
> the class path or module path?
It doesn't look like in its current form it's possible (without an
`--add-exports`) to have additional `java.util.random.RandomGenerator`
implementations in the class path (or module path). I tried some experiment
today to introduce a trivial `java.util.random.RandomGenerator` implementation
as follows:
package foo;
import java.util.Random;
import java.util.random.RandomGenerator;
public class DummyRandomGenerator implements RandomGenerator {
private final Random random = new Random();
@Override
public long nextLong() {
System.out.println("nextLong from " + this.getClass());
return random.nextLong();
}
}
Package this `DummyRandomGenerator` into a jar file and in that jar file
include a `META-INF/services/java.util.RandomGenerator` which points to the
`foo.DummyRandomGenerator` class. Then launch a main application with this jar
in the classpath:
import java.util.random.RandomGeneratorFactory;
public class Main {
public static void main(String[] args) {
System.out.println("available RandomGenerator(s):");
RandomGeneratorFactory.all().map(RandomGeneratorFactory::name).forEach(System.out::println);
}
}
Running this `Main` application with that jar in the classpath doesn't list the
`DummyRandomGenerator`. It appears that such application/library specific
implementations of `java.util.random.RandomGenerator` are expected to be
annotated to an annotation that belongs to the internals of the java.base
module
https://github.com/openjdk/jdk/blob/master/src/java.base/share/classes/java/util/random/RandomGeneratorFactory.java#L391.
Changing the `DummyRandomGenerator` to have it annotated with:
@jdk.internal.util.random.RandomSupport.RandomGeneratorProperties(name="Dummy")
public class DummyRandomGenerator implements RandomGenerator {
...
and then compiling that application class with:
javac --add-exports java.base/jdk.internal.util.random=ALL-UNNAMED ...
and then re-packaging that jar with this class and rerunning the Main with that
jar in the classpath will this time return the `DummyRandomGenerator` from a
call to `RandomGeneratorFactory.all()`.
The API docs of `java.util.random.RandomGeneratorFactory` don't make a mention
of the necessity of this internal
`jdk.internal.util.random.RandomSupport.RandomGeneratorProperties` annotation.
-------------
PR Comment: https://git.openjdk.org/jdk/pull/18932#issuecomment-2080455552
