Tomcat 5.5.x java.lang.NoClassDefFoundError: javax/servlet/http/HttpSessionListener

Tomcat 5.5.x) java.lang.NoClassDefFoundError:
javax/servlet/http/HttpSessionListener

Or

java.lang.NoClassDefFoundError: javax/servlet/ServletContextListener

for that matter.

NoClassDefFoundError on HttpSessionListener , ServletListener ,
ServletContextListener, etc. can be caused by a custom classloader
like Sysdeo DevLoader (I use it with Eclipse) in you Context
definition in the Tomcat's server.xml file.

the solution: add

useSystemClassLoaderAsParent="false"

to the Loader