How to run Docker with python and Java?

OK it took me a little while to figure it out. And my thanks go to this answer.

I think my approach didn't work because I did not have a basic version of Linux.

So it goes like this:

1. Get Linux (I'm using Alpine because it's barebones)
2. Get Java via the package manager
3. Get Python, PIP

OPTIONAL: find and set JAVA_HOME

4. Find the path to JAVA_HOME. Perhaps there is a better way to do this, but I did this running the running the container, then I looked inside the container using docker exec -it [COINTAINER ID] bin/bash and found it.
5. Set JAVA_HOME in dockerfile and build + run it all again

Here is the final Dockerfile ( it should work with the python code in the question) :

### 1. Get Linux
FROM alpine:3.7

### 2. Get Java via the package manager
RUN apk update \
&& apk upgrade \
&& apk add --no-cache bash \
&& apk add --no-cache --virtual=build-dependencies unzip \
&& apk add --no-cache curl \
&& apk add --no-cache openjdk8-jre

### 3. Get Python, PIP

RUN apk add --no-cache python3 \
&& python3 -m ensurepip \
&& pip3 install --upgrade pip setuptools \
&& rm -r /usr/lib/python*/ensurepip && \
if [ ! -e /usr/bin/pip ]; then ln -s pip3 /usr/bin/pip ; fi && \
if [[ ! -e /usr/bin/python ]]; then ln -sf /usr/bin/python3 /usr/bin/python; fi && \
rm -r /root/.cache

### Get Flask for the app
RUN pip install --trusted-host pypi.python.org flask

####
#### OPTIONAL : 4. SET JAVA_HOME environment variable, uncomment the line below if you need it

#ENV JAVA_HOME="/usr/lib/jvm/java-1.8-openjdk"

####

EXPOSE 81    
ADD test.py /
CMD ["python", "test.py"]

I'm new to Docker, so this may not be the best possible solution. I'm open to suggestions.

UPDATE: COMMON ISUUES

• Difficulty using python packages

As Joabe Lucena pointed out here, Alpine can have issues certain python packages. I recommend that you use a Linux distro that works best for you, e.g. centos.

Oh, let me add my five cents. I took python slim as a base image. Then I found open-jdk-11 (Note, open-jdk-10 will fail because it is not supported) base image code!... And copy-pasted it into my docker file.

Note, copy-paste driven development is cool... ONLY when you understand each line you use in your code!!!

And here it is!

<!-- language: shell -->
FROM python:3.7.2-slim

# Do your stuff, install python.

# and now Jdk
RUN rm -rf /var/lib/apt/lists/* && apt-get clean && apt-get update && apt-get upgrade -y \
    && apt-get install -y --no-install-recommends curl ca-certificates \
    && rm -rf /var/lib/apt/lists/*

ENV JAVA_VERSION jdk-11.0.2+7

COPY slim-java* /usr/local/bin/

RUN set -eux; \
    ARCH="$(dpkg --print-architecture)"; \
    case "${ARCH}" in \
       ppc64el|ppc64le) \
         ESUM='c18364a778b1b990e8e62d094377af48b000f9f6a64ec21baff6a032af06386d'; \
         BINARY_URL='https://github.com/AdoptOpenJDK/openjdk11-binaries/releases/download/jdk-11.0.1%2B13/OpenJDK11U-jdk_ppc64le_linux_hotspot_11.0.1_13.tar.gz'; \
         ;; \
       s390x) \
         ESUM='e39aacc270731dadcdc000aaaf709adae7a08113ccf5b4a045bc87fc13458d71'; \
         BINARY_URL='https://github.com/AdoptOpenJDK/openjdk11-binaries/releases/download/jdk-11%2B28/OpenJDK11-jdk_s390x_linux_hotspot_11_28.tar.gz'; \
         ;; \
       amd64|x86_64) \
         ESUM='d89304a971e5186e80b6a48a9415e49583b7a5a9315ba5552d373be7782fc528'; \
         BINARY_URL='https://github.com/AdoptOpenJDK/openjdk11-binaries/releases/download/jdk-11.0.2%2B7/OpenJDK11U-jdk_x64_linux_hotspot_11.0.2_7.tar.gz'; \
         ;; \
       aarch64|arm64) \
         ESUM='b66121b9a0c2e7176373e670a499b9d55344bcb326f67140ad6d0dc24d13d3e2'; \
         BINARY_URL='https://github.com/AdoptOpenJDK/openjdk11-binaries/releases/download/jdk-11.0.1%2B13/OpenJDK11U-jdk_aarch64_linux_hotspot_11.0.1_13.tar.gz'; \
         ;; \
       *) \
         echo "Unsupported arch: ${ARCH}"; \
         exit 1; \
         ;; \
    esac; \
    curl -Lso /tmp/openjdk.tar.gz ${BINARY_URL}; \
    sha256sum /tmp/openjdk.tar.gz; \
    mkdir -p /opt/java/openjdk; \
    cd /opt/java/openjdk; \
    echo "${ESUM}  /tmp/openjdk.tar.gz" | sha256sum -c -; \
    tar -xf /tmp/openjdk.tar.gz; \
    jdir=$(dirname $(dirname $(find /opt/java/openjdk -name javac))); \
    mv ${jdir}/* /opt/java/openjdk; \
    export PATH="/opt/java/openjdk/bin:$PATH"; \
    apt-get update; apt-get install -y --no-install-recommends binutils; \
    /usr/local/bin/slim-java.sh /opt/java/openjdk; \
    apt-get remove -y binutils; \
    rm -rf /var/lib/apt/lists/*; \
    rm -rf ${jdir} /tmp/openjdk.tar.gz;

ENV JAVA_HOME=/opt/java/openjdk \
    PATH="/opt/java/openjdk/bin:$PATH"
ENV JAVA_TOOL_OPTIONS="-XX:+UseContainerSupport"

Now references. https://github.com/AdoptOpenJDK/openjdk-docker/blob/master/11/jdk/ubuntu/Dockerfile.hotspot.releases.slim

https://hub.docker.com/_/python/

https://hub.docker.com/r/adoptopenjdk/openjdk11/

I used them to answer this question, which may help you sometime. Running Python and Java in Docker

An easier solution to the above issue is to use multi-stage docker containers where you can copy the content from one to another. In the above case you can have openjdk:slim as the base container and then use content from a python container to be copied over into this base container as follows:

FROM openjdk:slim
COPY --from=python:3.6 / /

... 

<normal instructions for python container continues>

...

This feature is available as of Docker 17.05 and there are more things you can do using multi-stage build as in copying only the content you need from one to another.

Reference documentation

Another alternative is to simply use docker-java-python image from docker hub. https://hub.docker.com/r/rappdw/docker-java-python

FROM rappdw/docker-java-python:openjdk1.8.0_171-python3.6.6
RUN java -version
RUN python --version