How to run Docker with python and Java?

Question

I need both java and python in my docker container to run some code.

This is my dockerfile: It works perpectly if I don't add the FROM openjdk:slim

#get python
FROM python:3.6-slim

RUN pip install --trusted-host pypi.python.org flask

#get openjdk

FROM openjdk:slim


COPY . /targetdir
WORKDIR /targetdir

# Make port 81 available to the world outside this container
EXPOSE 81

CMD ["python", "test.py"]

And the test.py app is in the same directory:

from flask import Flask

import os
app = Flask(__name__)


@app.route("/")

def hello():
    html = "<h3>Test:{test}</h3>"
    test = os.environ['JAVA_HOME']

    return html.format(test = test)


if __name__ == '__main__':
    app.run(debug=True,host='0.0.0.0',port=81)

I'm getting this error:

D:\MyApps\Docker Toolbox\Docker Toolbox\docker.exe: Error response from daemon: OCI runtime create failed: container_linux.go:348: starting container process caused "exec: \"python\": executable file not found in $PATH": unknown.

What exactly am I doing wrong here? I'm new to docker, perhaps I'm missing a step.

Additional details

My goal

I have to run a python program that runs a Java file. The python library I'm using requires the path to JAVA_HOME.

My issues:

• I do not know Java, so I cannot run the file properly.

• My entire code is in Python, except this Java bit

• The Python wrapper runs the file in a way I need it to run.

Answer 1

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

Answer 2

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.

Answer 3

you should have one FROM in your dockerfile (unless you use multi-stage build for the docker)

Answer 4

I believe that by adding FROM openjdk:slim line, you tell docker to execute all of your subsequent commands in openjdk container (which does not have python)

I would approach this by creating two separate containers for openjdk and python and specify individual sets of commands for them.

Docker is made to modularize your solutions and mashing everything into one container is usually a bad practice.

Answer 5

Instead of using FROM openjdk:slim you can separately install Java, please refer below example:

# Install OpenJDK-8
RUN apt-get update && \
apt-get install -y openjdk-8-jdk && \
apt-get install -y ant && \
apt-get clean;

# Fix certificate issues
RUN apt-get update && \
apt-get install ca-certificates-java && \
apt-get clean && \
update-ca-certificates -f;
# Setup JAVA_HOME -- useful for docker commandline
ENV JAVA_HOME /usr/lib/jvm/java-8-openjdk-amd64/
RUN export JAVA_HOME

Answer 6

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