At least one JAR was scanned for TLDs yet contained no TLDs

As soon as I added a jar to my Tomcat base web application, I got this new info log message.

INFO [main] org.apache.jasper.servlet.TldScanner.scanJars
At least one JAR was scanned for TLDs yet contained no TLDs

It makes sense, since it was a JDBC driver, and I would have been very surprised if it contained a TLD.

Let's see how to get rid of it.

Firstly, I read the rest of the logging message

Enable debug logging for this logger for a complete list
of JARs that were scanned but no TLDs were found in them.
Skipping unneeded JARs during scanning can
improve startup time and JSP compilation time.

Actually, I already knew the name of the JAR culprit, since I just added it, so I could have skipped directly to the second step. However, I followed the instructions and ...

Tomcat logging properties

I (temporarily) changed the logging.properties for my Tomcat instance, adding this line

org.apache.jasper.servlet.TldScanner.level = FINE

After that, my log file got more interesting, and I focused my attention to this line.

FINE [main] org.apache.jasper.servlet.TldScanner$TldScannerCallback.scan
No TLD files were found in [... x.jar] Consider adding the
JAR to the tomcat.util.scan.StandardJarScanFilter.jarsToSkip
property in CATALINA_BASE/conf/catalina.properties file.

Very clear indeed.

Tomcat Catalina properties

I easily found the tomcat.util.scan.StandardJarScanFilter.jarsToSkip property in file catalina.properties from my Tomcat configuration folder. It is a longish comma separated string containing a list of JAR that are known not to contain TLD.

I just added the name of my JAR to it, and the case was closed.