There is documentation in the [SLf4J][1] site which resolves this issue. Follow that and add `slf4j-simple-1.7.29.jar` to your application along with `slf4j-api-1.7.29.jar`.
**SLF4J Simple Binding » 1.7.29**
<!-- https://mvnrepository.com/artifact/org.slf4j/slf4j-simple --> <dependency> <groupId>org.slf4j</groupId> <artifactId>slf4j-simple</artifactId> <version>1.7.29</version> <scope>test</scope> </dependency>
**SLF4J API Module » 1.7.29**
<!-- https://mvnrepository.com/artifact/org.slf4j/slf4j-api --> <dependency> <groupId>org.slf4j</groupId> <artifactId>slf4j-api</artifactId> <version>1.7.29</version> </dependency>
Hope this helps you and others who have this issue.
[1]: http://www.slf4j.org/codes.html#StaticLoggerBinder

Quite a few answers here recommend adding the slf4j-simple dependency to your maven pom file. You might want to check for the most current version.
At https://mvnrepository.com/artifact/org.slf4j/slf4j-simple you'll find the latest version of the SLF4J Simple Binding. Pick the one that suites you best (still 1.7.26 from 2019-02 is the stable version as of 2019-07) and include it to your pom.xml.
For your convenience some dependencies are shown here - but they might not be up-to-date when you read this!
**Alpha Version of 2019-06**
<!-- https://mvnrepository.com/artifact/org.slf4j/slf4j-simple --> <dependency> <groupId>org.slf4j</groupId> <artifactId>slf4j-simple</artifactId> <version>2.0.0-alpha0</version> </dependency>
**Beta Version of Feb 2019**
<!-- https://mvnrepository.com/artifact/org.slf4j/slf4j-simple --> <dependency> <groupId>org.slf4j</groupId> <artifactId>slf4j-simple</artifactId> <version>1.8.0-beta4</version> </dependency>
**Stable Version 2019-08**
<!-- https://mvnrepository.com/artifact/org.slf4j/slf4j-simple --> <dependency> <groupId>org.slf4j</groupId> <artifactId>slf4j-simple</artifactId> <version>1.7.28</version> <scope>test</scope> </dependency>
I removed the scope test part thanks to the comment below.