Is KeyCloak 7.0.1 compatible with OpenJDK 13?
As per the document the software installation pre-requisite should be OpenJDK 8, which is quite old version.
To my knowledge, Keycloak 7 stream is based on WildFly 17 which doesn’t support OpenJDK 13. Starting with WildFly 18, there is support for OpenJDK 13:
JDK 13
Our goal with WildFly is to have our releases run well for most use cases on the most recent GA JDK version available on the WildFly final release date. I’m pleased to report that this is the case with WildFly 18 and JDK 13. By run well, I mean the main WildFly testsuite runs with no more than a few failures in areas not expected to be commonly used. We want developers who are trying to evaluate what the latest JVM means for their applications to be able to look to WildFly as a useful development platform.
While we do want to run well on the most recent JDK, our recommendation is that you run WildFly on the most recent long-term support release, i.e. on JDK 11 for WildFly 18. We do considerably more testing of WildFly itself on the LTS JDKs, and we make no attempt to ensure the projects producing the various libraries we integrate are testing their libraries on anything other than JDK 8 or 11.
WildFly 18 also is heavily tested and runs well on Java 8. We plan to continue to support Java 8 at least through WildFly 21, and probably beyond.
Please note that WildFly runs on Java 11 and later in classpath mode.
At this point it is uncertain whether we’ll be able to say that the release of WildFly that follows JDK 14 going GA will run well on 14. We’ll have to see how well the work for that, both in WildFly itself and in the projects we integrate, aligns with our other goals for that release.
Keycloak itself is built with OpenJDK 11. At least that’s what I can tell from the Tavis CI build.