将外壳打开到Java映像中

Question

I'm building a postgres+java container, and I'd like to open a shell into the java "service". That service exits immediately after starting, how can I do to open a shell into it?

I see it in docker ps -a but it has already exited.

The file I'm using is this .yaml with docker-compose

version: '3.1'

services:

  db:
    image: postgres
    restart: always
    environment:
      POSTGRES_PASSWORD: postgres
    volumes:

      - datavolume:/var/lib/postgresql


  java:

    image: openjdk:8

volumes:

  datavolume:

Answer 1

A Docker container generally runs a single process. In the same way that just running a JVM without an application attached to it isn't really meaningful, running a Docker container with a JVM but no actual application added to it isn't that useful.

You should write a Dockerfile that adds your application's jar file to a base Java image; for instance

FROM openjdk:8
COPY app.jar /
CMD ["java", "-jar", "/app.jar"]

and then your docker-compose.yml file can have instructions to build and run this image

services:
  java:
    build: .

If you just want a shell in a copy of the image to poke around and see what's there, you can generally run

docker run --rm -it openjdk:8 sh

The standard openjdk Dockerfile doesn't explicitly declare any specific ENTRYPOINT or CMD so it will exit immediately when run. (It probably inherits a default /bin/sh , but with no command to run, that will also exit immediately.) You can declare some other command: in the Dockerfile to cause the "service" to not exit, but it's not really doing anything useful for you.