在Dockerfile中编写java时如何在容器中安装java？

Question

I am naive in software development. I want to run a jar file from Dkron Scheduler using cron job. I am running dkron in docker(using docker-compose up). I am passing "command": "java --version" to see if I can run java from Dkron. As docker do not have java installed I changed the dockerfile.hub file to this:

FROM alpine
LABEL maintainer="Victor Castell <victor@victorcastell.com>"

RUN set -x \
    && buildDeps='bash ca-certificates openssl tzdata' \ 
    && apk add --update $buildDeps \
    && apk add openjava8                                #add this line to install java
    && rm -rf /var/cache/apk/* \
    && mkdir -p /opt/local/dkron

ENV JAVA_HOME /usr/lib/jvm/java-1.8-openjdk             #add this line to install java
ENV PATH $PATH:$JAVA_HOME/bin                           #add this line to install java

EXPOSE 8080 8946

ENV SHELL /bin/bash
WORKDIR /opt/local/dkron

COPY dkron .
COPY dkron-* ./
ENTRYPOINT ["/opt/local/dkron/dkron"]

CMD ["--help"]

When I again do docker-compose up it do not give any error, still on passing "command": "java --version" by json through UI, dkron shows error - exec : "java" : executable file not found in $PATH.

What can I do to resolve it?

Thanks in advance.

Answer 1

I was able to create JVM in docker container using dkron as the base image, (publically available) and build another image on top of it.

Here is dockerfile I created for running java application

FROM dkron/dkron
WORKDIR /root/hello-world
COPY hello.java /root/hello-world

RUN apk add openjdk8

ENV JAVA_HOME /usr/lib/jvm/java-1.8-openjdk
ENV PATH $JAVA_HOME/bin:$PATH

RUN javac hello.java

Then I build image. Let id be xxx Then I ran the image and build dkron server as docker run -p 8080:8080 xxx agent --server --bootstrap-expect=1 --node-name=node1

Answer 2

Try this file

FROM alpine
LABEL maintainer="Victor Castell <victor@victorcastell.com>"

RUN set -x \
        && buildDeps='bash ca-certificates openssl tzdata' \
        && apk add --update $buildDeps \
        && apk add openjdk8 \
        && rm -rf /var/cache/apk/* \
        && mkdir -p /opt/local/dkron

ENV JAVA_HOME=/usr/lib/jvm/java-1.8-openjdk
ENV PATH="$JAVA_HOME/bin:${PATH}"

EXPOSE 8080 8946

ENV SHELL /bin/bash
WORKDIR /opt/local/dkron

COPY dkron .
COPY dkron-* ./
ENTRYPOINT ["/opt/local/dkron/dkron"]

CMD ["--help"]

alpine package doesn't have openjava8 packages.

Edit: Update ENV variables