servletcontext.log filename

[Rob Sargent]

I'm using an embedded tomcat (ver9.0.54) and I don't see how to 
name/redirect the output of ServletContext.log(String).

I see in the manual
   This logging is performed according to the Tomcat logging
   configuration. You cannot overwrite it in a web application.

I missing the "Tomcat logging config" bit, I guess.