Akka Quickstart: An illegal reflective access operation has occurred

When running the official Akka Quickstart on my Mac terminal, I get this error:

Getting org.scala-sbt sbt 1.2.8 ...
WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by org.apache.ivy.util.url.IvyAuthenticator (file:/Users/helios/eclipse-workspace/akka-quickstart-java/sbt-dist/bin/sbt-launch.jar) to field java.net.Authenticator.theAuthenticator
WARNING: Please consider reporting this to the maintainers of org.apache.ivy.util.url.IvyAuthenticator
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release
reStart

Is this the intended result? How can I go about fixing this?

Answer

This is a warning, not an error.

Here is a quote from Oracle JDK 9 Migration Guide

https://docs.oracle.com/javase/9/migrate/toc.htm#JSMIG-GUID-7BB28E4D-99B3-4078-BDC4-FC24180CE82B

Understanding Runtime Access Warnings

Some tools and libraries use reflection to access parts of the JDK that are meant for internal use only. This illegal reflective access will be disabled in a future release of the JDK. In JDK 9, it is permitted by default and a warning is issued.

For example, here is the warning issued when starting Jython:

java -jar jython-standalone-2.7.0.jar
WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by jnr.posix.JavaLibCHelper (file:/C:/Jython/jython2.7.0/jython-standalone-2.7.0.jar) to method sun.nio.ch.SelChImpl.getFD()
WARNING: Please consider reporting this to the maintainers of jnr.posix.JavaLibCHelper
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release
Jython 2.7.0 (default:9987c746f838, Apr 29 2015, 02:25:11)

If you see a warning like this, contact the maintainers of the tool or library. The second line of the warning names the exact JAR file whose code used reflection to access an internal part of the JDK.

By default, a maximum of one warning about reflective access is issued in the lifetime of the process started by the java launcher. The exact timing of the warning depends on the behavior of tools and libraries performing reflective–access operations. The warning may appear early in the lifetime of the process, or a long time after startup.

You can disable the warning message on a library-by-library basis by using the --add-opens command line flag.