A Java agent for fixing exports for an app that is not yet Java 9 aware.

WeakeningAgent.java

import java.lang.instrument.Instrumentation;
import java.lang.reflect.Layer;
import java.lang.reflect.Module;
import java.util.*;

public class WeakeningAgent {

    public static void premain(String argument, Instrumentation instrumentation) {
        boolean full = argument != null && argument.equals("full");
        Set<Module> importing = new HashSet<>(), exporting = new HashSet<>();
        Layer.boot().modules().forEach(module -> {
            if (module.getDescriptor().isAutomatic()) {
                importing.add(module);
            } else if (!module.getDescriptor().isWeak()) {
                exporting.add(module);
            }
        });
        for (Module module : exporting) {
            Map<String, Set<Module>> exports = new HashMap<>();
            for (String pkg : module.getPackages()) {
                exports.put(pkg, importing);
            }
            instrumentation.redefineModule(module,
                    Collections.emptySet(),
                    full ? exports : Collections.emptyMap(),
                    exports,
                    Collections.emptySet(),
                    Collections.emptyMap());
        }
    }
}