/usr/share/maven-repo/org/eclipse/jetty/websocket/javax-websocket-server-impl/ is in libjetty9-extra-java 9.2.21-1+deb9u1.
This file is owned by root:root, with mode 0o755.
..
/usr/share/maven-repo/org/eclipse/jetty/websocket/javax-websocket-server-impl/9.2.21.v20170120/
/usr/share/maven-repo/org/eclipse/jetty/websocket/javax-websocket-server-impl/9.2.21.v20170120/javax-websocket-server-impl-9.2.21.v20170120.jar
/usr/share/maven-repo/org/eclipse/jetty/websocket/javax-websocket-server-impl/9.2.21.v20170120/javax-websocket-server-impl-9.2.21.v20170120.pom
/usr/share/maven-repo/org/eclipse/jetty/websocket/javax-websocket-server-impl/debian/
/usr/share/maven-repo/org/eclipse/jetty/websocket/javax-websocket-server-impl/debian/javax-websocket-server-impl-debian.jar
/usr/share/maven-repo/org/eclipse/jetty/websocket/javax-websocket-server-impl/debian/javax-websocket-server-impl-debian.pom