title: Set Level for all java.util.logging Loggers programmatically
body: <p>I work on an application which uses slf4j and log4j2 as the underlying logging framework. The application provides custom logging filters, based on the current user of the application. Some third party libraries use <code>java.util.logging</code> (JUL) internally. I would like those logs to also submit to my user based filter. I.e. while the default log level may be <code>ERROR</code>, I can configure the application to log on level <code>DEBUG</code> when an specific user is using it.</p>
  
  <p>Therefore I integrated the <a href="https://www.slf4j.org/legacy.html" rel="nofollow noreferrer">jul-to-slf4j</a> bridge so that JUL logging is redirected to slf4j. I've also created a custom java.util.logging.Filter <a href="https://stackoverflow.com/questions/33867514/jul-to-slf4j-for-specific-classes-only">as described here</a> which implements my user based filter logic.</p>
  
  <p>Now my problem is that the default log level in JUL seems to be <code>INFO</code> and there also is logic which first checks if the message to log has an less fine level than the level of the logger, in which case the message is rejected immediatly without passing through the filter (in this case my custom filter). Because of this I want all JUL Loggers (also the ones used in third party libraries) to by default have the level <code>ALL</code> so that all JUL log statements would pass through my filter where it would be determined wether to log the message or to discard it. </p>
  
  <p>I've tried setting the JULs root logger and it's handlers level to <code>ALL</code> as it is described in multiple posts here on SO, but this didn't seem to make the trick <a href="https://stackoverflow.com/questions/54786116/java-util-logging-logger-has-different-level-than-its-root-logger">as seen here</a>. It looks like I have to configure the JUL <code>LogManager</code> accordingly and I wonder if I can do so programatically without introducing a new log file?</p>