Dockerfile Spring Boot property from variable not working

Question

I can't seem to get Spring boot properties to work via variable in my Dockerfile. This is what I am doing:

ENTRYPOINT exec java -Dapp-version=$app_version -jar /app.jar

If I do RUN echo "App Version: $app_version" inside of my Dockerfile then I get then I get the correct output like App Version: 1.70.0.

If I manually put the version like this: ENTRYPOINT exec java -Dapp-version=1.70.0 -jar /app.jar then the value is injected correctly.

In fact, if I do RUN echo "ENTRYPOINT exec java -Dapp-version=$app_version -jar /app.jar" then I get output like

Step 9/10 : RUN echo "ENTRYPOINT exec java -D******ion=$app_version -jar /app.jar"
 ---> Running in b6c3cd9bb69a
ENTRYPOINT exec java -D******ion=1.70.0 -jar /app.jar

The value inside of Spring is being set as an empty string when I use the Dockerfile variable. When I hard code it to 1.70.0 then it is being set correctly. What am I missing?

I have tried many different things including using {}, quotes, etc.

Edit: Added Dockerfile

FROM java:8
ARG app_version

RUN echo -------------------
RUN echo "App Version: $app_version"
RUN echo -------------------

VOLUME /tmp
COPY ./build/libs/mango-sticky-rice-1.0.0-SNAPSHOT.jar /app.jar
RUN bash -c 'touch /app.jar'

ENTRYPOINT exec java -Dapp-version=$app_version -jar /app.jar

check out this answer https://stackoverflow.com/a/37904830/3711885 — Amine Zaine, Nov 21 '19 at 22:37
I actually already saw that answer and my entry point is already setup that way. It is injecting an empty string instead of the actual version because I have a default value inside of my application.yaml file that is being overwritten. My entry point is using the shell form already. — Gremash, Nov 21 '19 at 22:44
Have you hardcoded a value to see if gets read in your Java app? — Chol Nhial, Nov 21 '19 at 22:48
Yes. If I hard code the value then it is injected correctly into my Spring Boot app. — Gremash, Nov 21 '19 at 22:50
How are you setting the variable `app_version`, is it in `pom.xml`? — Chol Nhial, Nov 21 '19 at 22:58
docker build --build-arg app_version=<< parameters.app_version >>. This is part of my CircleCI build config. I am 100% sure the value is being passed in because I am echoing it out and am also doing the same thing in a Node project. — Gremash, Nov 21 '19 at 23:01
@Gremash, you're not calling a shell that's gonna expand the env vars, replace `exec` by `sh -c` — Amine Zaine, Nov 21 '19 at 23:09
ENTRYPOINT bash -c 'java -Dapp-version=$app_version -jar /app.jar'. That didn't work. I got the same result. — Gremash, Nov 21 '19 at 23:20
I think you need to use double quotes for string variable substitution, but give my answer a shot, it's shell neutral. — Chol Nhial, Nov 21 '19 at 23:23

score 0 · Accepted Answer · answered Nov 21 '19 at 23:43

This answer worked: https://stackoverflow.com/a/49889134/3088642. This is what my Dockerfile looks like:

FROM java:8
ARG app_version

RUN echo -------------------
RUN echo "App Version: ${app_version}"
RUN echo -------------------

VOLUME /tmp
COPY ./build/libs/mango-sticky-rice-1.0.0-SNAPSHOT.jar /app.jar
RUN bash -c 'touch /app.jar'

RUN echo "#!/bin/bash \n java -Dapp-version=${app_version} -jar /app.jar" > ./entrypoint.sh
RUN chmod +x ./entrypoint.sh

RUN cat ./entrypoint.sh

ENTRYPOINT ["./entrypoint.sh"]

Dockerfile Spring Boot property from variable not working

1 Answers1