If I try to create a InitialContext object in a method of an JSP extension tag I retrieve the following exception:

javax.naming.NoInitialContextException: Cannot instantiate class: com.sun.jndi.fscontext.RefFSContextFactory. Root exception is java.lang.ClassNotFoundException ....

The InitialContext creation (and lookup) is regularly performed in a servlet. The jar of FSContext Provider is available.

Thanks for any help.
Angelo