Using logback, but somehow log4j getting initialized

Question

Our console application is using logback for logging. There's a logback.xml file in the classpath.

Logging works as expected (via logback) on most platforms (Linux, Windows, jdk7 or jdk8).

However, on Macs using jdk 6, when running the app we sometimes see:

log4j:WARN No appenders could be found for logger (our.class.Here).
log4j:WARN Please initialize the log4j system properly.

It seems for some reason log4j is chosen for logging instead of logback. In our.class.Here we log through slf4j:

private static final org.slf4j.Logger LOG = org.slf4j.LoggerFactory.getLogger(our.class.Here.class);

This is the complete classpath:

/path/etc/logback.xml:/path/lib/pdfbox-1.8.4.jar:/path/lib/fontbox-1.8.4.jar:/path/lib/jempbox-1.8.4.jar:/path/lib/jcl-over-slf4j-1.7.7.jar:/path/lib/bcprov-jdk15-1.45.jar:/path/lib/bcmail-jdk15-1.45.jar:/path/lib/xmlgraphics-commons-1.5.jar:/path/lib/icepdf-core-5.0.4.jar:/path/lib/jai-codec-1.1.3.jar:/path/lib/jai-core-1.1.3.jar:/path/lib/jewelcli-0.6.jar:/path/lib/commons-lang3-3.1.jar:/path/lib/commons-io-2.2.jar:/path/lib/logback-classic-1.1.0.jar:/path/lib/logback-core-1.1.0.jar:/path/lib/itext-2.1.7.jar:/path/lib/hibernate-validator-4.2.0.Final.jar:/path/lib/slf4j-api-1.7.5.jar

How could we troubleshoot further to understand why log4j instead of logback is chosen for logging?

Thanks for your suggestions.

Alex Alex · Accepted Answer · 2015-01-20T16:43:26

I don't see log4j-over-slf4j in your classpath... perhaps that's what you're missing to ensure any log4j related code goes through the proper slf4j logging impl (logback)?

  <dependency>
    <groupId>org.slf4j</groupId>
    <artifactId>log4j-over-slf4j</artifactId>
    <version>1.7.10</version>
  </dependency>

Using logback, but somehow log4j getting initialized

2 Answers