org.slf4j.LoggerFactory-logs to SystemOut even if configured to log to a specific file:jar conflict?

[Francesco Bellini]

Hello,

I'm experiencing some issue with the logger slf4j which is being used into sever classes into my project.
Even if I configured the logger in order to write into a specific file, it prints into SystemOut.log.

I am pretty sure it could be a jar conflict, but I cannot figure out what jar can be removed and what jar has to stay there.

Here's the list of the (logging) jars I am using in the project:
slf4j-api-1.6.4.jar
log4j-1.2.15.jar
commons-logging-1.2.jar
logback-classic-1.0.0.jar


Even if I change the appender-ref, only to go to a specific appender (RollingFileAppender - to another file), it doesn't work.

Can somebody help me to debug such a mess please?

[Rob Spoor]

You're missing the bridge between SLF4J and Log4J (slf4j-log4j12-1.6.4.jar).

Just a hint by the way: upgrade to at least version 1.7. That added varargs so you don't have to manually create arrays if you want to have more than 2 arguments to your logging methods.

[Francesco Bellini]

Thanks a lot Rob,

I've added slf4j-log4j12-1.7.12 as dependency, and upgraded slf4j-api to 1.7.12 as well.
Nothing has changed yet, but this is what I can see in the Console when the webapp starts:


SLF4J: Class path contains multiple SLF4J bindings.
SLF4J: Found binding in [jar:file:/apache-tomcat-7.0.34/wtpwebapps/webapp-test/WEB-INF/lib/logback-classic-1.0.0.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: Found binding in [jar:file://apache-tomcat-7.0.34/wtpwebapps/webapp-test/WEB-INF/lib/slf4j-log4j12-1.7.12.jar!/org/slf4j/impl/StaticLoggerBinder.class]
SLF4J: See http://www.slf4j.org/codes.html#multiple_bindings for an explanation.

Of course, I've already performed a search on google about it, but after many attempts, I wasn't able to solve.
Removing logback-classic from my pom.xml causes no logging at all both in systemout and the log file configured.

[Rob Spoor]

Do you have Log4J configured to do any logging?

[Francesco Bellini]

Yes, of course:

here's the log file:
<?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE log4j:configuration SYSTEM "log4j.dtd"> <log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/"> <appender name="webappTestAppender" class="org.apache.log4j.RollingFileAppender"> <param name="File" value="D:/temp/logs/webappTest.log"/> <param name="MaxFileSize" value="10000KB"/> <param name="MaxBackupIndex" value="3"/> <param name="Append" value="true"/> <layout class="org.apache.log4j.PatternLayout"> <param name="ConversionPattern" value="%d [%t] %p - %m%n"/> </layout> </appender> <appender name="console" class="org.apache.log4j.ConsoleAppender"> <param name="Target" value="System.out"/> <layout class="org.apache.log4j.PatternLayout"> <param name="ConversionPattern" value="%d [%t] %p - %m%n"/> </layout> </appender> <root> <level value="INFO" /> <appender-ref ref="console"/> <appender-ref ref="webappTestAppender"/> </root> </log4j:configuration>

EDIT: this is what I see after removing logback-classic from the pom.xml file.
log4j:WARN No appenders could be found for logger (org.springframework.web.context.ContextLoader).
log4j:WARN Please initialize the log4j system properly.

This is a spring-mvc web application by the way.

[Francesco Bellini]

After playing a little bit within the web.xml configuration and removing logback-classic, I figured out how to get the logger working:

<listener> <listener-class>org.springframework.web.util.Log4jConfigListener</listener-class> </listener> <context-param> <param-name>log4jConfigLocation</param-name> <param-value>file:///${webapp.root.config}/log4j.xml</param-value> </context-param>