Support OpenJDK 11+ (Java 11+)

Allowing people running XMage on OpenJDK 11+ would involve many steps: (UPDATE: expect this list to be updated dynamically)

• Replace sun.reflect.generics.reflectiveObjects.ParameterizedTypeImpl (#5862, #6380)
• Stop using deprecated (later removed) Look and Feel classes (#6394)
• Update the Update the JBoss/Wildfly serialisation infrastructure (#6514, #6531)
• Add OpenJFX dependencies so the code can be compiled under OpenJDK11+ (#6703 - not merged yet)
• Fix Java 9+ packages compatible (javac does not detect split packages between classpath and system image, e.g. org.w3c.dom problem #6809)
• Add OpenJFX libs to client assembly (#6818)
• Migrate to Java 9+ modules system (module-info.java) (#6820)
• Update Travis CI config to work with OpenJDK 11+ (#6779)
• Update the Launcher so it does allow to use a local JDK/JRE, instead of an old, unsopported Oracle JDK8 (#5723, #6462)
• Update the README and documentation to officially support only JDK11+
• Inform XMage’s third party servers about OpenJDK 11 migration before new release (e.g. by news website)

[ldeluigi]

Done this:

Update the Launcher so it does allow to use a local JDK/JRE, instead of an old, unsopported Oracle JDK8

Here: https://github.com/magefree/Launcher/pull/14

[allentiak]

Project must be migrated to [the Java module system]

Eventually, yes.

For now, #6703’s https://github.com/magefree/mage/commit/1764f13b96e64a8db8a553a037d65a3eabd72129 makes the code work as-is. You will find a link to the relevant Java bug in the commit message.