Maven SLF4J: Class path contains multiple SLF4J bindings

Run mvn dependency:tree and search which dependency have the slf4j implementations you do not want, then exclude them with a dependency exclusion like:

<dependency>
    <groupId>org.someexternallib</groupId>
    <artifactId>someexternallibartifact</artifactId>
    <version>...</version>

    <exclusions>
       <exclusion> 
          <groupId>org.slf4j</groupId>
          <artifactId>slf4j-log4j12</artifactId>
       </exclusion>
       <exclusion> 
          <groupId>log4j</groupId>
          <artifactId>log4j</artifactId>
      </exclusion>
    </exclusions> 
</dependency>