SLF4J warning or error messages and their meanings
The method
o.a.commons.logging.impl.SLF4FLogFactory#release
was invoked.
Given the structure of the commons-logging API, in particular
as implemented by SLF4J, the
o.a.commons.logging.impl.SLF4FLogFactory#release()
method should never be called. However, depending on the
deployment of commons-logging.jar files in your servlet
container, release()
may be unexpectedly invoked by a
copy of org.apache.commons.logging.LogFactory
class
shipping with commons-logging.jar.
This is a relatively common occurrence with recent versions of Tomcat, especially if you place jcl104-over-slf4j.jar in WEB-INF/lib directory of your web-application instead of $TOMCAT_HOME/common/lib, where $TOMCAT_HOME stands for the directory where Tomcat is installed. In order to fully benefit from the stability offered by jcl104-over-slf4j.jar, we recommend that you place jcl104-over-slf4j.jar in $TOMCAT_HOME/common/lib without placing a copy in your web-applications.
Please also see bug #22.
Failed to load class
org.slf4j.impl.StaticLoggerBinder
This error is reported when the
org.slf4j.impl.StaticLoggerBinder
class could not be
loaded into memory. This happens when no appropriate SLF4J
binding could be found on the class path. Placing one (and only
one) of slf4j-nop.jar, slf4j-simple.jar,
slf4j-log4j12.jar, slf4j-jdk14.jar or
logback-classic.jar on the class path should solve the
problem.
Logging factory implementation cannot be null
This error is reported when the LoggerFactory
class could not find an appropriate binding. Placing one (and only
one) of slf4j-nop.jar, slf4j-simple.jar,
slf4j-log4j12.jar, slf4j-jdk14.jar or
logback-classic.jar on the class path should prove to be
an effective remedy.
Failed to load class "org.slf4j.impl.StaticMDCBinder".
This error indicates that appropriate SLF4J binding could be found on the class path. Placing one (and only one) of slf4j-nop.jar, slf4j-simple.jar, slf4j-log4j12.jar, slf4j-jdk14.jar or logback-classic.jar on the class path should solve the problem.
MDCAdapter cannot be null
This error is reported when org.slf4j.MDC
class
has not been initialized correctly. Same cause and remedy as the
previously listed item.