Caused by: java.lang.Error: This version of SLF4J requires log4j version 1.2.12 or later.

I recently synched up to a project to make a new build and upon deployment I encountered a frustrating error:

Caused by: java.lang.Error: This version of SLF4J requires log4j version 1.2.12 or later.

This issue was a real pain, because the error message was very misleading. Basically, the error message is complaining that I don't have a log4j version 1.2.12 or greater.

I checked my classpath, performed a cleaned build, cleared my tomcat cache and restarted tomcat, and none of them fixed the issue. Indeed, my log4j version 1.2.14!!

Bah, I started to dig deeper into the issue and it boiled down to this:

I had replace

        <dependency>
            <groupId>org.slf4j</groupId>
            <artifactId>slf4j-log4j12</artifactId>
            <version>1.5.0</version>
        </dependency>

With:

    <dependency>
        <groupId>org.slf4j</groupId>
        <artifactId>slf4j-api</artifactId>
        <version>1.5.6</version>
    </dependency>     
                        
    <dependency>
        <groupId>org.slf4j</groupId>
        <artifactId>slf4j-simple</artifactId>
        <version>1.5.6</version>
    </dependency>   

I hope this saves somebody else hours of pain