I have a black box application that runs on old obsolete Jetty 7.
However, it has been working well since we installed it in 2014, and I
need it to continue running. I have been asked to add an X-Frame-Options
header to the interface, and every time I try to do this by changing
Java I get class incompatibility errors. I can, however, make any
changes I like to the JSP files, to web.xml, or to the Jetty
configuration files in jetty/etc, but so far I have not found a change
that works. I tried adding