KeyCloak Server Caused by: java.lang.ClassNotFoundException: java.security.acl.Group at

问题

I'm running a KeyCloak server to authenticate users which would like to gain access a SpringBoot-Web RestAPI. However, I an error occurs while trying to authenticate.

The following works:

When I access my http://localhost:8080/path/to/restapi
I get presented with a login screen as expected: -- KeyCloak Login Screen
When I click login the following error occurs on the redirect from within my browser:

Whitelabel Error Page This application has no explicit mapping for /error, so you are seeing this as a fallback.

Error on my Spring-Boot output console:

Caused by: java.lang.ClassNotFoundException: java.security.acl.Group
    at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:602) ~[na:na]
    at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:178) ~[na:na]
    at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:522) ~[na:na]
    ... 33 common frames omitted

The KeyCloak server shows that the session is active for the user to the application. However, the authenication process is never completed due to the above missing class.

回答1:

After some research I found the answer to my problem.

The problem is that java.security.acl.Group is being deprecated since JRE 9 and marked for removal in future versions.

java.security.acl.Group is being replaced by java.security.Policy

I was running my Spring-Boot application on JRE 14 in which this class appeared to be no longer available.

So once I changed my Spring-boot application (which hosts the REST-API) to use JRE 11 the error went away.

Note: The pom.xml Java version attibute <java.version>11</java.version> needed to change as well as the JDK in the build path in Eclipse (which is the IDE I'm using) JDK Buildpath