jsp - Tomcat 8 enable debug logging to list unneeded jars

Question

When starting Tomcat 8 on Arch Linux ARM I get the following warning:

INFO: 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.`

I already modified ${catalina.home}/logging.properties like described here: How to fix JSP compiler warning: one JAR was scanned for TLDs yet contained no TLDs?

I changed some logging levels from INFO to FINE, uncommented "org.apache.jasper.compiler.TldLocationsCache.level = FINE" and added "org.apache.jasper.servlet.TldScanner.level = FINE". So the end of the file now looks the following:

org.apache.catalina.core.ContainerBase.[Catalina].[localhost].level = FINE org.apache.catalina.core.ContainerBase.[Catalina].[localhost].handlers = 2localhost.org.apache.juli.AsyncFileHandler

org.apache.catalina.core.ContainerBase.[Catalina].[localhost].[/manager].level = FINE org.apache.catalina.core.ContainerBase.[Catalina].[localhost].[/manager].handlers = 3manager.org.apache.juli.AsyncFileHandler

org.apache.catalina.core.ContainerBase.[Catalina].[localhost].[/host-manager].level = FINE org.apache.catalina.core.ContainerBase.[Catalina].[localhost].[/host-manager].handlers = 4host-manager.org.apache.juli.AsyncFileHandler

# For example, set the org.apache.catalina.util.LifecycleBase logger to log # each component that extends LifecycleBase changing state: #org.apache.catalina.util.LifecycleBase.level = FINE

# To see debug messages in TldLocationsCache, uncomment the following line: org.apache.jasper.compiler.TldLocationsCache.level = FINE org.apache.jasper.servlet.TldScanner.level = FINE

But I still get the warning at startup and not the unneeded JAR's paths. What's wrong?

Answer 1

Try debugging for everything by:

1. Adding this to the end of your logging.properties file located in {CATALINA-HOME}/conf:

   #To see the most detailed level of logging for all classes, uncomment the following line:
   org.apache.catalina.level=FINEST
   

2. Restart Tomcat

3. Run the following from Terminal to get a list of jars that need to be skipped (courtesy of @joseph-lust on this post):

   egrep "No TLD files were found in [file:[^]+]" {CATALINA-HOME}/logs/catalina.out -o | egrep "[^]/]+.jar" -o | sort | uniq | sed -e 's/.jar/.jar,\/g' > ~/skips.txt
   

4. Open skips.txt in your user home directory

5. Add this list to {CATALINA-HOME}/conf/catalina.properties after the following line:

   org.apache.catalina.startup.TldConfig.jarsToSkip=
   

6. Make sure to remove/comment out this when you are done to prevent your log files from growing too large

I am still not sure why this happens, as it seems to work for most to uncomment the TldLocationsCache line.