java.lang.ClassNotFoundException: org.slf4j.LoggerFactory

You get this error because you forgot to add required JARs into the application classpath (sidenote: this is happening when you do not use Maven or Gradle and try to manage your JARs manually).

---

Q: How to solve it?

A: Add required JARs into the classpath.

---

Q: Where to find required JARs?

A: In the ZIP file in libs directory, as described on the project main page.

---

More details can be found here:

How to solve java.lang.ClassNotFoundException: org.slf4j.LoggerFactory