Using Oracle’s JDK in CircleCI (with Gradle)

I’m evaluating re-writing Dashman in Java (instead of Electron). It’s too early to tell, but so far all the experiments and the early re-write are going well and it’s solving the issues I was having with Electron. This short post is about CircleCI.

Because now I’m using common, boring technologies, I decided setting a CI was going to be easy enough that I didn’t mind doing it and I chose CircleCI, mostly because of their free plan.

Sadly, my project didn’t work out of the box. JavaFX was nowhere to be found. The reason was that CircleCI uses OpenJDK instead of the Oracle’s JDK by default. I guess that’s enough for the vast majority of people. Switching to Oracle’s JDK was not hard, but I couldn’t find a straightforward post, so, this is it.

CircleCI gives you a configuration example that contains something like this:

version: 2
  jobs:
    build:
      docker:
        # specify the version you desire here
        - image: circleci/openjdk:8-jdk

I’m not very familiar with Docker and how CircleCI uses, all I know is that it’s a container system for, essentially, operating system images. CircleCI has a repo of Docker images and the one that include’s Oracle’s JDK is called circleci/jdk8. What comes after the colon in the config is the version of the Docker image (I think) which Docker calls tags and for this one, at the time of this writing, there was 0.1.1 but you can easily check the latest one here: https://hub.docker.com/r/circleci/jdk8/tags/

With that in mind, the config should now look like this:

version: 2
  jobs:
    build:
      docker:
        # specify the version you desire here
        - image: circleci/jdk8:0.1.1

And that’s it… well, unless you are using Gradle. That image doesn’t provide Gradle, so, you need to replace all the mentions of gradle with gradlew and use the wrapper that should be part of your repo. But before that will work, you need to make that file executable on the CircleCI server by calling chmod +x gradlew on it. The resulting config file for me looks like this:

# Java Gradle CircleCI 2.0 configuration file
#
# Check https://circleci.com/docs/2.0/language-java/ for more details
#
version: 2
jobs:
  build:
    docker:
      # specify the version you desire here
      - image: circleci/jdk8:0.1.1

      # Specify service dependencies here if necessary
      # CircleCI maintains a library of pre-built images
      # documented at https://circleci.com/docs/2.0/circleci-images/
      # - image: circleci/postgres:9.4

    working_directory: ~/repo

    environment:
      # Customize the JVM maximum heap limit
      JVM_OPTS: -Xmx3200m
      TERM: dumb

    steps:
      - checkout
      - run: chmod +x gradlew

      # Download and cache dependencies
      - restore_cache:
          keys:
          - v1-dependencies-{{ checksum "build.gradle" }}
          # fallback to using the latest cache if no exact match is found
          - v1-dependencies-

      - run: ./gradlew dependencies

      - save_cache:
          paths:
            - ~/.m2
          key: v1-dependencies-{{ checksum "build.gradle" }}

      # run tests!
      - run: ./gradlew test

And that’s it, that worked.

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