ClassNotFoundException: org.slf4j.LoggerFactory

Better to always download as your first try, the most recent version from the developer's site

I had the same error message you had, and by downloading the jar from the above (slf4j-1.7.2.tar.gz most recent version as of 2012OCT13), untarring, uncompressing, adding 2 jars to build path in eclipse (or adding to classpath in comand line):

1. slf4j-api-1.7.2.jar
2. slf4j-simple-1.7.2.jar

I was able to run my program.

Try downloading jar from here

You can find, it holds the class you need.

EDIT

Seems like the website has changed its structure. You need to choose which jar file you need for your project.

For slf4j-api jar file for latest version as of now, please visit this link

For slf4j-simple jar file for latest version as of now, please visit this link

For a bit more explanation: keep in mind that the "I" in "api" is interface. The slf4j-api jar only holds the needed interfaces (actually LoggerFactory is an abstract class). You also need the actual implementations (an example of which, as noted above, can be found in slf4j-simple). If you look in the jar, you'll find the required classes under the "org.slf4j.impl" package.