How to pass Java_opts before an executable to entrypoint in dockerfile?

You can declare environment variables with ENV:

...
ADD --chown=daemon:daemon UserPrefExporter.sc /opt/docker
USER daemon
ENV JAVA_OPTS="-Xmx<limit>"
ENTRYPOINT ["./amm", "-h", "amm_home", "UserPrefExporter.sc"]

This post suggests using explicit exec in ENTRYPOINT:

ENTRYPOINT exec java $JAVA_OPTS