If someone is using Maven and is having the same issue while assembling a flat jar, here is what I did to fix the same issue:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-shade-plugin</artifactId>
<version>3.2.1</version>
<executions>
<execution>
<phase>package</phase>
<goals>
<goal>shade</goal>
</goals>
<configuration>
<transformers>
<transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
<mainClass>foo.bar.Generate</mainClass>
<manifestEntries>
<Multi-Release>true</Multi-Release>
</manifestEntries>
</transformer>
<transformer implementation="org.apache.maven.plugins.shade.resource.ServicesResourceTransformer"/>
</transformers>
</configuration>
</execution>
</executions>
</plugin>
The important part is <Multi-Release>true</Multi-Release>
.
Note that the Java code I’m using now to change loggers level is:
Configurator.setAllLevels("foo.bar", Level.DEBUG);