Spring Boot exectuable jar Dockerfile with JAVA_OPTS, debugging and JRebel support

Dockerfile

# Used as a base image that other Spring Boot-based
# docker containers can be based off of. Example dependent Dockerfile:
#
#     FROM <this-image>
#     ADD target/myjar.jar /app.jar
#
# Alternatively, you can modify this file to use a build arg:
#     ...
#     ...
#     ARG JAR_FILE
#     ADD ${JAR_FILE} app.jar
# 
# and then build with:
#      
#     docker build --build-arg JAR_FILE=target/myjar.jar .
# 
# This image can be built in 2 modes:
# 1. Normal - assumes an /app.jar is present as a fat Spring-Bootified jar file (executes with java -jar)
# 2. Jrebel - also downloads the Jrebel agent embedded in the image. An image with the JRebel agent downloaded
# can set a JREBEL environment variable (must be a non-empty string) to activate the Jrebel JVM parameters.
# This relies on JRebel remoting and a rebel-remote.xml built into the /app.jar

FROM openjdk:8u151-jdk-alpine
VOLUME /tmp
ADD run-app.sh run-app.sh
RUN chmod +x run-app.sh

ADD wait-for.sh wait-for.sh
RUN chmod +x wait-for.sh

# Only downloads jrebel if the argument is set
ARG JREBEL
ENV JREBEL=${JREBEL}
ADD download-jrebel.sh download-jrebel.sh
RUN chmod +x download-jrebel.sh && ./download-jrebel.sh

ENTRYPOINT ./run-app.sh

download-jrebel.sh

if [ -z ${JREBEL} ]; then
  echo "Set the JREBEL argument to download and use JRebel remoting inside the container"
else
  apk --no-cache add wget unzip
  wget http://dl.zeroturnaround.com/jrebel-stable-nosetup.zip
  unzip jrebel-stable-nosetup.zip
fi

run-app.sh

if [ "$DEBUG_PORT" ]; then
  export JAVA_OPTS="$JAVA_OPTS -agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=$DEBUG_PORT"
fi

if [ "$JREBEL" ]; then
  export JREBEL_ARGS="-agentpath:jrebel/lib/libjrebel64.so -Drebel.remoting_plugin=true"
  export JAVA_OPTS="$JAVA_OPTS $JREBEL_ARGS"
fi

# Moved into a shell script because the above 'export' statements cannot be retrieved
# between multiple statements in a Dockerfile
echo "Starting Java with the arguments $JAVA_OPTS"
java $JAVA_OPTS -Djava.security.egd=file:/dev/./urandom -jar /app.jar