$ sudo apt-get update
$ sudo apt-get install libjnlp-servlet-java 

libjnlp-servlet-java is installed in your system.

Make ensure the libjnlp-servlet-java package were installed using the commands given below,

$ sudo dpkg-query -l | grep libjnlp-servlet-java *

You will get with libjnlp-servlet-java package name, version, architecture and description in a table

libjnlp-servlet-java package basic information: