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.

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.