At least one JAR was scanned for TLDs Message On Server Start

Question

There is a message in catalina log, like

...

03-Jan-2020 10:35:50.659 INFO [localhost-startStop-3] org.apache.jasper.servlet.TldScanner.scanJars At least one JAR was scanned for TLDs yet contained no TLDs. 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.

...

Could you please clarify if it may affect performance somehow (this scanning) and how it's possible to disable this scan/message?

Explanation

Apache Tomcat has the default list of JAR files that should not be scanned using the JarScanner functionality which is typically used to scan JARs for configuration information.

JARs that do not contain such information may be excluded from the scan to speed up the scanning process:

 https://tomcat.apache.org/tomcat-8.0-doc/config/jar-scanner.html Default list of JAR files that should not be scanned using the JarScanner functionality specified in /conf/catalina.properties config file.

tomcat.util.scan.StandardJarScanFilter.jarsToSkip

property.

In order to get details of the JARs without TLD information, you can add property

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

to /conf/logging.properties config file, stop Apache Tomcat, clear work folder and start it again.

As a result, catalina.xxx.log file will contain details of affected JARs like

org.apache.jasper.servlet.TldScanner$TldScannerCallback.scan 
No TLD files were found in
 [file:/D:/Jaspersoft/jasperreports-server-7.2.0/apache-tomcat/webapps/jasperserver-pro/WEB-INF/lib/jasperreports-highcharts-7.3.0_MOD.jar]

Then, the JARs can be added to the list of Jars to skip: tomcat.util.scan.StandardJarScanFilter.jarsToSkip

If you use Tomcat v.7.x you may need to apply another solution:

 stackoverflow.com/questions/14375673/how-to-fix-jsp-compiler-warning-one-jar-was-scanned-for-tlds-yet-contained-no-t/45751740 

In order to disable JarScanner for a specific web-application, you should add the JarScanner element as a child of the root Context element in the META-INF/context.xml file

Solution tested with TIBCO JasperReports^® Server v.7.2.0

AS-20200227, case 01824970