gamussa / spring-boot-jib-workbench

A workbench project how to use the Jib gradle plugin to create docker images for Spring Boot applications in Kotlin.

Spring Boot / Kotlin / Gradle / Jib Workbench

…​ what it’s for

Demonstrate how to use the Jib Gradle Plugin to create a docker container.

Jib offers a new approach in generating Docker images for Java applications by by separating libraries, classes and resources into separate layers which speeds up deployment and reduces the size of the image layers that change often during application development. You can read more about Jib on the Jib GitHub Project page.

In addition the gradle script contains all necessary setup to use Kotlin and Spring Boot 2 for the implementation.

Note	Due to a problem in Version 0.9.8 of Jib it is not possible to use the openjdk base image. By default Jib uses gcr.io/distroless/java.

…​ how it’s setup

In order to be able to push the generated docker image to a registry you need to set the dockerRegistryPrefix property in the gradle.properties file. In case of the Docker Hub registry this is your username. By default the Jib plugin will use the authentication mechanism and credentials provided by the configuration of your docker configuration (for example ~/.docker/config.json)

The deployments folder contains a simple kubernetes deployment descriptor for this application. You have to update the image name in order to use your image.

…​ how it’s build

Build and push an image by issuing gradle jib.

To build the image and create a local Docker daemon use gradle jibDockerBuild.

…​ how it’s structured

The Gradle build script is split into multiple files that can be found in the gradle folder:

jib.gradle

Configures the Jib plugin.

kotlin.gradle

Is responsible for all things related to Kotlin.

test.gradle

Sets up Gradle to use JUnit 5 to run tests.

…​ what it can do

Since the purpose of the project is to demonstrate the build mechanism the application itself only provides two simple endpoints at /smoke and /burn.

In addition the Spring Actuator package is included in the application.