I have a logback.xml. A fragment of it is:
<filter name="FileAppenderThresholdFilter"
class="ch.qos.logback.classic.filter.ThresholdFilter">
<level>${LOGGER_SDK_FILE_APPENDER_LOGLEVEL:-OFF}</level>
</filter>

If I obtain the ThresholdFilter object from java code, the name of it is null. I am sure I find the right object.