many url-pattern for the same servlet

I guess it has more to do with the servlet spec the container/netbeans is using rather than being an issue with the container. Your net beans seems to be using the spec 2.5 to construct the servlet mapping and hence you get

<servlet-mapping>
   <servlet-name>fred</servlet-name>
   <url-pattern>*.jsp</url-pattern>
   <url-pattern>/url</url-pattern>
</servlet-mapping>

Read more about this here. It says

Previous versions of the servlet schema allows only a single url-pattern in a
filter mapping.For filters mapped to multiple URLs this results in needless
repetition of whole mapping clauses.