Spring PetClinic Sample Application

This is an example application showcasing how to run a Java app on CircleCI 2.0. This application uses the Spring PetClinic sample project.

This readme includes pared down sample configs for different CircleCI features, including workspace, dependency caching, and parallelism.

Version 2.1

To see how we would use orbs to checkout, build, and test in one line, please see the 2.1-orbs-config branch.

To see these features in a version 2.1 config with reusable commands and running on different executors, please see the 2.1-simplified-config branch.

Sample configurations: version 2.0

• A basic build
• Using a workflow to build then test
• Caching dependencies
• Persisting build artifacts to workspace
• Splitting tests across parallel containers
• Storing code coverage artifacts
• All together

A basic build

version: 2.0

jobs:
  build:
    docker:
      - image: circleci/openjdk:stretch
    steps:
      - checkout
      - run: ./mvnw package

Version 2.0 configs without workflows will look for a job entitled build. A job is a essentially a series of commands run in a clean execution environment. Notice the two primary parts of a job: the executor and steps. In this case, we are using the docker executor and passing in a CCI convenience image.

Using a workflow to build then test

version: 2.0

jobs:
  test:
    docker:
      - image: circleci/openjdk:stretch
    steps:
      - checkout
      - run: ./mvnw test

  build:
    docker:
      - image: circleci/openjdk:stretch
    steps:
      - checkout
      - run: ./mvnw -Dmaven.test.skip=true package

workflows:
  version: 2

  build-then-test:
    jobs:
      - build
      - test:
          requires:
            - build

A workflow is a dependency graph of jobs. This basic workflow runs a build job followed by a test job. The test job will not run unless the build job exits successfully.

Caching dependencies

version: 2.0

jobs:
  build:
    docker:
      - image: circleci/openjdk:stretch
    steps:
      - checkout
      - restore_cache:
          keys:
            - v1-dependencies-{{ checksum "pom.xml" }} # appends cache key with a hash of pom.xml file
            - v1-dependencies- # fallback in case previous cache key is not found
      - run: ./mvnw -Dmaven.test.skip=true package
      - save_cache:
            paths:
              - ~/.m2
            key: v1-dependencies-{{ checksum "pom.xml" }}

The first time I ran this build without any dependencies cached, it took 2m14s. Once I was able to just restore my dependencies, the build took 39 seconds.

Note that the restore_cache step will restore whichever cache it first matches. I add a restore key here as a fallback. In this case, even if pom.xml changes, I can still restore the previous cache. This means my job will only have to fetch the dependencies that have changed between the new pom.xml and the previous cache.

Persisting build artifacts to workspace

version: 2.0

jobs:
  build:
    docker:
      - image: circleci/openjdk:stretch
    steps:
      - checkout
      - run: ./mvnw -Dmaven.test.skip=true package
      - persist_to_workspace:
         root: ./
         paths:
           - target/

  test:
    docker:
      - image: circleci/openjdk:stretch
    steps:
      - checkout
      - attach_workspace:
          at: ./target
      - run: ./mvnw test

workflows:
  version: 2

  build-then-test:
    jobs:
      - build
      - test:
          requires:
            - build

This special step allows you to persist files or directories to be used by downstream jobs in the workflow. In this case, the target directory produced by the build step is persisted for use by the test step.

Splitting tests across parallel containers

version: 2.0

jobs:
  test:
    parallelism: 2 # parallel containers to split the tests among
    docker:
      - image: circleci/openjdk:stretch
    steps:
      - checkout
      - run: |
          ./mvnw \
          -Dtest=$(for file in $(circleci tests glob "src/test/**/**.java" \
          | circleci tests split --split-by=timings); \
          do basename $file \
          | sed -e "s/.java/,/"; \
          done | tr -d '\r\n') \
          -e test
      - store_test_results: # We use this timing data to optimize the future runs
          path: target/surefire-reports

  build:
    docker:
      - image: circleci/openjdk:stretch
    steps:
      - checkout
      - run: ./mvnw -Dmaven.test.skip=true package

workflows:
  version: 2

  build-then-test:
    jobs:
      - build
      - test:
          requires:
            - build

Splitting tests by timings is a great way to divide time-consuming tests across multiple parallel containers. I think of splitting by timings as requiring 4 parts:

1. a list of tests to split
2. the command: circleci tests split --split-by=timings
3. containers to run the tests
4. historical data to intelligently decide how to split tests

To collect the list of tests to split, I simply pulled out all of the Java test files with this command: circleci tests glob "src/test/**/**.java". Then I used sed and tr to translate this newline-separated list of test files into a comma-separated list of test classes.

Adding store_test_results enables CircleCI to access the historical timing data for previous executions of these tests, so the platform knows how to split tests to achieve the fastest overall runtime.

Storing code coverage artifacts

version: 2.0

jobs:
  test:
    docker:
      - image: circleci/openjdk:stretch
    steps:
      - checkout
      - run: ./mvnw test verify
      - store_artifacts:
          path: target/site/jacoco/index.html

workflows:
  version: 2

  test-with-store-artifacts:
    jobs:
      - test

The Maven test runner with the JaCoCo plugin generates a code coverage report during the build. To save that report as a build artifact, use the store_artifacts step.

All together

version: 2.0

jobs:
  test:
    parallelism: 2
    docker:
      - image: circleci/openjdk:stretch
    steps:
      - checkout
      - restore_cache:
          keys:
            - v1-dependencies-{{ checksum "pom.xml" }}
            - v1-dependencies-
      - attach_workspace:
          at: ./target
      - run: |
            ./mvnw \
            -Dtest=$(for file in $(circleci tests glob "src/test/**/**.java" \
            | circleci tests split --split-by=timings); \
            do basename $file \
            | sed -e "s/.java/,/"; \
            done | tr -d '\r\n') \
            -e test verify
      - store_test_results:
          path: target/surefire-reports
      - store_artifacts:
          path: target/site/jacoco/index.html

  build:
    docker:
      - image: circleci/openjdk:stretch
    steps:
      - checkout
      - restore_cache:
          keys:
            - v1-dependencies-{{ checksum "pom.xml" }}
            - v1-dependencies-
      - run: ./mvnw -Dmaven.test.skip=true package
      - save_cache:
          paths:
            - ~/.m2
          key: v1-dependencies-{{ checksum "pom.xml" }}
      - persist_to_workspace:
         root: ./
         paths:
           - target/

workflows:
  version: 2

  build-then-test:
    jobs:
      - build
      - test:
          requires:
            - build

All of these features can be used in a single config file to optimize your build.