/usr/share/maven-repo/org/eclipse/jetty/jetty-alpn-server/9.2.21.v20170120/jetty-alpn-server-9.2.21.v20170120.jar is in libjetty9-java 9.2.21-1+deb9u1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/share/maven-repo/org/eclipse/jetty/jetty-alpn-server/9.2.21.v20170120/../../../../../../java/jetty9-alpn-server.jar