/usr/lib/eclipse/plugins/javax.servlet_3.1.0.jar is in eclipse-platform 3.8.1-11.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/eclipse/plugins/../../../share/java/servlet-api-3.1.jar
/usr/lib/eclipse/plugins/../../../share/java/servlet-api-3.1.jar