datanucleus-enhancer is a java agent that manipulates java classes during jvm startup. It uses a Log4J binding, which is implemented by slf4j and delegated to logback.
datanucleus-enhacer spams the console with unnecessary debug statements while it does its work:

21:29:25.369 [main] DEBUG DataNucleus.ClassLoading - Class "org.eclipse.core.runtime.RegistryFactory" was not found in the CLASSPATH [Class resolver called from org.datanucleus.plugin.PluginRegistryFactory.newInstance (line=91)]
21:29:25.374 [main] DEBUG DataNucleus.Plugin - Plugin Registry "org.datanucleus.plugin.EclipsePluginRegistry" not found. Falling back to DataNucleus registry. Reason : Class "org.eclipse.core.runtime.RegistryFactory" was not found in the CLASSPATH. Please check your specification and your CLASSPATH..
21:29:25.375 [main] DEBUG DataNucleus.Plugin - Using PluginRegistry org.datanucleus.plugin.NonManagedPluginRegistry
21:29:25.399 [main] DEBUG DataNucleus.ClassLoading - Class "org.eclipse.core.runtime.RegistryFactory" was not found in the CLASSPATH [Class resolver called from org.datanucleus.plugin.PluginRegistryFactory.newInstance (line=91)]
21:29:25.400 [main] DEBUG DataNucleus.Plugin - Plugin Registry "org.datanucleus.plugin.EclipsePluginRegistry" not found. Falling back to DataNucleus registry. Reason : Class "org.eclipse.core.runtime.RegistryFactory" was not found in the CLASSPATH. Please check your specification and your CLASSPATH..
21:29:25.400 [main] DEBUG DataNucleus.Plugin - Using PluginRegistry org.datanucleus.plugin.NonManagedPluginRegistry
...
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That is because logback does not find my logback.xml on the classpath:
<configuration>
<appender name="console"
class="de.invesdwin.gemeinsam.log.logback.ConfiguredConsoleAppender">
<Target>System.err</Target>
</appender>
<root level="WARN">
<appender-ref ref="console" />
</root>
</configuration>

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This is caused by ContextInitializer.getResource() using the wrong classloader during java agent process:
sun.misc.Launcher$AppClassLoader@28df6ccd

which cannot resolve the classpath name:
logback.xml

to fix this, logback should fallback to the system classloader if the resource was not found with the specific classloader. To do this, we have to change:
-------------------
private URL getResource(String filename, ClassLoader myClassLoader, boolean updateStatus) {
URL url = Loader.getResource(filename, myClassLoader);
if (updateStatus)

{ statusOnResourceSearch(filename, myClassLoader, url); }
return url;
}
-------------------
to:
-------------------
private URL getResource(String filename, ClassLoader myClassLoader, boolean updateStatus) {
URL url = Loader.getResource(filename, myClassLoader);
if(url == null){ url = Loader.getResource(filename, ClassLoader.getSystemClassLoader()); }
if (updateStatus) { statusOnResourceSearch(filename, myClassLoader, url); }

return url;
}

to properly initialize logback during javaagent execution.