I'm new to Java EE and trying to work on ServletContextListener and listener job is connection to database bla bla .When I am trying to start the server (Tomcat 9) it is stuck on :
"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."
So I changed some properties in "Logging properties file" like this :
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# this work for additional information regarding copyright ownership.
# The ASF licenses this file to You under the Apache License, Version 2.0
# (the "License"); you may not use this file except in compliance with
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handlers = 1catalina.org.apache.juli.AsyncFileHandler, 2localhost.org.apache.juli.AsyncFileHandler, 3manager.org.apache.juli.AsyncFileHandler, 4host-manager.org.apache.juli.AsyncFileHandler, java.util.logging.ConsoleHandler
.handlers = 1catalina.org.apache.juli.AsyncFileHandler, java.util.logging.ConsoleHandler
############################################################
# Handler specific properties.
# Describes specific configuration info for Handlers.
############################################################
1catalina.org.apache.juli.AsyncFileHandler.level = FINE
1catalina.org.apache.juli.AsyncFileHandler.directory = ${catalina.base}/logs
1catalina.org.apache.juli.AsyncFileHandler.prefix = catalina.
2localhost.org.apache.juli.AsyncFileHandler.level = FINE
2localhost.org.apache.juli.AsyncFileHandler.directory = ${catalina.base}/logs
2localhost.org.apache.juli.AsyncFileHandler.prefix = localhost.
3manager.org.apache.juli.AsyncFileHandler.level = FINE
3manager.org.apache.juli.AsyncFileHandler.directory = ${catalina.base}/logs
3manager.org.apache.juli.AsyncFileHandler.prefix = manager.
4host-manager.org.apache.juli.AsyncFileHandler.level = FINE
4host-manager.org.apache.juli.AsyncFileHandler.directory = ${catalina.base}/logs
4host-manager.org.apache.juli.AsyncFileHandler.prefix = host-manager.
java.util.logging.ConsoleHandler.level = FINE
java.util.logging.ConsoleHandler.formatter = org.apache.juli.OneLineFormatter
############################################################
# Facility specific properties.
# Provides extra control for each logger.
############################################################
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
# To see debug messages for HTTP/2 handling, uncomment the following line:
#org.apache.coyote.http2.level = FINE
# To see debug messages for WebSocket handling, uncomment the following line:
#org.apache.tomcat.websocket.level = FINE
All answers acceptable. Thanks for all.
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.
On startup, Tomcat recursively scans the WEB-INF directories for TLD (Tag Library Descriptor) files. As a result, if a webapp has a lot of files under that directory, it slows down the startup process.
If you want to redistribute your tag files or implement your custom tags with tag handlers written in Java, you must declare the tags in a tag library descriptor (TLD). A tag library descriptor is an XML document that contains information about a library as a whole and about each tag contained in the library.
This is not a bug or any kind of problem in tomcat. Tomcat is just informing you that there are jars that do not contain TLDs and you can add them to the scanner's skip list to improve startup performance. So you have two options:
You can safely ignore that hint. Yet if it annoy you, you can set that specific logger to a higher logging level, and thus prevent tomcat from logging it. Just add org.apache.jasper.servlet.TldScanner.level = SEVERE
to the end of logging.properties.
Enable the debug logging to make tomcat list those jars and add them to the skip list. Set:
org.apache.jasper.compiler.TldLocationsCache.level = FINE
org.apache.jasper.servlet.TldScanner.level = FINE
And add the printed jars names (without the path) to tomcat.util.scan.StandardJarScanFilter.jarsToSkip=...
in tomcat_dir/conf/catalina.properties
Setting the logging to FINE, FINEST or ALL to find all jars to exclude is not neccessary.
Here is a script that finds all jars not containing TLDs (change the TOMCAT_HOME variable to match your installation) and outputs a list on the form
jar1.jar,\
jar2.jar,\
...
that can be pasted into catalina.properties (omit the last ',\'):
#!/bin/sh
TOMCAT_HOME=/opt/tomcat
for i in `find $TOMCAT_HOME -follow -name "*jar"`
do
jar tvf $i | grep -i tld > /dev/null
if [ $? -ne 0 ]; then
echo "$(basename $i),\\"
fi
done
However, if I am correctly informed, there is a possibility in tomcat 9 to exclude all jars by changing (in catalina.properties):
tomcat.util.scan.StandardJarScanFilter.jarsToSkip=\
to
tomcat.util.scan.StandardJarScanFilter.jarsToSkip=*.jar
(comment away the list on the lines below) and then override that decision for jars containg TLDs by changing:
tomcat.util.scan.StandardJarScanFilter.jarsToScan=\
log4j-web*.jar,log4j-taglib*.jar,log4javascript*.jar,slf4j-taglib*.jar
and add the list obtained by modifying the script above to list the jars that do contain TLDs:
#!/bin/sh
TOMCAT_HOME=/opt/tomcat
for i in `find $TOMCAT_HOME -follow -name "*jar"`
do
jar tvf $i | grep -i tld > /dev/null
if [ $? -eq 0 ]; then
echo "$(basename $i),\\"
fi
done
change conf\context.xml file
<Context>
<!-- only if you do not use jsp tag -->
<JarScanner>
<JarScanFilter defaultPluggabilityScan="false" defaultTldScan="false"/>
</JarScanner>
</Context>
see: https://tomcat.apache.org/tomcat-9.0-doc/config/jar-scan-filter.html
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