title: KeyCloak Server Caused by: java.lang.ClassNotFoundException: java.security.acl.Group
body: <p>I'm running a KeyCloak server to authenticate users who would like to gain access to a Spring Boot/Spring Web REST API. However, an error occurs while trying to authenticate.</p>
  <p>The following works:</p>
  <ul>
  <li>When I access <code>http://localhost:8080/path/to/restapi</code></li>
  <li>I get presented with a login screen as expected:
  -- <a href="https://i.stack.imgur.com/JQdUw.png" rel="noreferrer">KeyCloak Login Screen </a></li>
  <li>When I click login the following error occurs on the redirect from within my browser:</li>
  </ul>
  <blockquote>
  <p>Whitelabel Error Page
  This application has no explicit mapping for /error, so you are seeing this as a fallback.</p>
  </blockquote>
  <p>This is the error that's printed to the Spring Boot console:</p>
  <pre class="lang-java prettyprint-override"><code>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
  </code></pre>
  <p>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.</p>