I have a java program which uses JBPM.
When I execute it, I encounter the following error:

....
javax.naming.NoInitialContextException: Cannot instantiate class:
org.jnp.interfaces.NamingContextFactory [Root exception is java.lang.ClassNotFoundE
xception: org.jnp.interfaces.NamingContextFactory]
....
java.lang.ClassNotFoundException: org.jnp.interfaces.NamingContextFactory

What have I do in order to solve the problem?!