Run jar file in docker image

Question

I created a Docker image with java, and am copying the jar file into the image. My Dockerfile is :

FROM anapsix/alpine-java
MAINTAINER myNAME 
COPY testprj-1.0-SNAPSHOT.jar /home/testprj-1.0-SNAPSHOT.jar
RUN java -jar /home/testprj-1.0-SNAPSHOT.j

After executing following command :

docker build -t imageName.

In the console I see the output from the application and everything is fine. But when I stop the image, I don`t know how to run the image again ? When I execute the following command :

docker run -i -t imageName java -jar /home/testprj-1.0-SNAPSHOT.jar

The application runs again, but in my Dockerfile I have already written this command. How can I run the image without this command and have the application run automatically?

Answer 1

There is a difference between images and containers.

• Images will be build ONCE
• You can start containers from Images

In your case:

Change your image:

FROM anapsix/alpine-java
MAINTAINER myNAME 
COPY testprj-1.0-SNAPSHOT.jar /home/testprj-1.0-SNAPSHOT.jar
CMD ["java","-jar","/home/testprj-1.0-SNAPSHOT.jar"]

Build your image:

docker build -t imageName .

Now invoke your program inside a container:

docker run --name myProgram imageName

Now restart your program by restarting the container:

docker restart myProgram

Your program changed? Rebuild the image!:

docker rmi imageName
docker build -t imageName .

Answer 2

This may not be quite what you asked, but if you just need to run a JAR (rather than that being just one part of a larger custom container) I like this approach of mapping a volume/folder to the JAR and running it using a standard upstream image:

docker run --rm -it -v /home/me/folderHoldingJar:/home:Z java:latest /bin/bash -c '/usr/bin/java -jar /home/theJarFile.jar'

There is even some additional args you can add if the JAR needs to display a GUI.