FULL PRODUCT VERSION :
java version "9-ea"
Java(TM) SE Runtime Environment (build 9-ea+174)
Java HotSpot(TM) Server VM (build 9-ea+174, mixed mode, emulated-client)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows [Version 6.1.7601]

A DESCRIPTION OF THE PROBLEM :
As proposed by Mark Reinhold
 http://mail.openjdk.java.net/pipermail/jigsaw-dev/2017-May/012673.html
there is a last-minute command-line option available for enabling/disabling/debugging Jigsaw visibility problems.

This flag --illegal-access=permit/warn/debug/deny needs to be whitelisted on the Web Start side to be passed through to the Java launcher

REGRESSION. Last worked in version 9

ADDITIONAL REGRESSION INFORMATION:
java version "9-ea"
Java(TM) SE Runtime Environment (build 9-ea+174)
Java HotSpot(TM) Server VM (build 9-ea+174, mixed mode, emulated-client)

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
1. Compile the attached file to a JAR file
2. Sign the jar, add a DeploymentRuleSet rule to allow running
3. Start the application as a Web Start app

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The application should run, printing warnings to the console
ACTUAL -
The application does not run, does not print any warnings

ERROR MESSAGES/STACK TRACES THAT OCCUR :
java.lang.reflect.InaccessibleObjectException: Unable to make field private final java.util.Comparator java.util.TreeMap.comparator accessible: module java.base does not "opens java.util" to unnamed module @9718a5
at java.base/java.lang.reflect.AccessibleObject.checkCanSetAccessible(Unknown Source)
at java.base/java.lang.reflect.AccessibleObject.checkCanSetAccessible(Unknown Source)
at java.base/java.lang.reflect.Field.checkCanSetAccessible(Unknown Source)
at java.base/java.lang.reflect.Field.setAccessible(Unknown Source)
at OpenModuleTest.main(OpenModuleTest.java:10)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.base/java.lang.reflect.Method.invoke(Unknown Source)
at jdk.javaws@9-ea/com.sun.javaws.Launcher.executeApplication(Unknown Source)
at jdk.javaws@9-ea/com.sun.javaws.Launcher.executeMainClass(Unknown Source)
at jdk.javaws@9-ea/com.sun.javaws.Launcher.doLaunchApp(Unknown Source)
at jdk.javaws@9-ea/com.sun.javaws.Launcher.run(Unknown Source)
at java.base/java.lang.Thread.run(Unknown Source)


REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
test.jnlp

=======
<?xml version="1.0" encoding="utf-8"?>
  <jnlp spec="6.0+" codebase="http://www.example.com/webstart" href="test.jnlp">
    <information>
      <title>Test app</title>
      <vendor>Anon</vendor>
      <offline-allowed/>
    </information>
    <security>
        <all-permissions/>
    </security>
    <update check="always" policy="always" />
    <resources>
      <j2se version="1.9" java-vm-args="--illegal-access=debug"/>
      <jar href="test.jar" main="true"/>
    </resources>

    <application-desc main-class="OpenModuleTest"/>
  </jnlp>


OpenModuleTest.java
=================

import java.lang.reflect.Field;
import java.util.Comparator;
import java.util.TreeMap;

public class OpenModuleTest {
     public static void main(String[] args) {
        System.err.println("Testing stderr");
         for (Field field : TreeMap.class.getDeclaredFields()) {
             if (field.getType() == Comparator.class) {
                 field.setAccessible(true);
                 break;
             }

         }

         System.out.println("OK");
     }
}


---------- END SOURCE ----------