Currently, it's not possible to compile JSPs compiling Java 8 idiom's as the version of the Jetty compiler used by Maven only supports Java 7 source.
Once Jetty has been upgraded to Jetty 9.3.6 or higher (see ), it should be possible to set the sourceVersion/targetVersion for the Jetty Jspc Maven Plugin - https://www.eclipse.org/jetty/documentation/current/jetty-jspc-maven-plugin.html
See https://github.com/igniterealtime/Openfire/pull/1059 for a PR containing a JSP that could contain a Java 8 idiom, in particular a anonymous lambda.
I thought this ticket should cover a workaround until Jetty is updated, but it soinds differently from the description. Am i missing something?
AFAICT, there is no work-around other than to not use Java 8 syntax.