Keycloak 18.0.0 - Installation problems

Getting advice
1

Hi,
I am sorry for this “noob” question. But I am new to Java and this topic.
I would like to install the most recent version Keycloak 18.0.0. all tutorials I found refer to a “standalone” file, which does not exist anymore. Following the origin docs did not work… I am getting the following error message:

"Error: A JNI error has occurred, please check your installation and try again

Exception in thread “main” java.lang.UnsupportedClassVersionError: io/quarkus/bootstrap/runner/QuarkusEntryPoint has been compiled by a more recent version of the Java Runtime (class file version 55.0), this version of the Java Runtime only recognizes class file versions up to 52.0"

How can I fix this. I am not sure if this is a problem of my Java Distribution (17) or Keyclaok.

Would be great to get any hint, where to look for a solution.
Regards Felix

2

This thread can be closed. The issue was, the my JAVA_HOME was still set to an older JAVA version. Now its running.

3

Just in case anyone else encounters this like I did as well, I’d like to clarify that the issue is referencing the JDK (Java Development Kit) and NOT the JRE (Java Runtime Environment) – these are two separate installations.

I didn’t realize it, but I did not have the JDK installed on my machine yet, so I had to install that and then update the JAVA_HOME environment variable to the JDK install location; in my case this was C:\Program Files\Java\jdk-18.0.1.1

Edit Side note – The OpenJDK “Getting Started” option does specify this: OpenJDK - Keycloak… I just didn’t read that page lol

4

I had this happen and it took a while to fix.

I installed OpenJDK 11, but something happened that had it replaced with an older version. For whatever reason my package manager was not letting me replace with the newer version, it just would not update the /bin/java (or whatever) path. I had to uninstall all OpenJDK packages and then manually install the correct OpenJDK package and it finally resolved.