Java: jar not loaded. See Servlet Spec 2.3, section 9.7.2. Offending class: javax/servlet/Servlet.class

Error: jar not loaded. See Servlet Spec 2.3, section 9.7.2. Offending class: javax/servlet/Servlet.class

Solution: Delete all the libs/jars that is duplicating the classes

Check this types of files: *.jar, *.zip, *.rar *.7z

Example

servlet-api.jar
servlet-api-5.5.15.jar
javax.servlet-3.0.jar