This project demonstrates how to use JKube Plugins to perform additional actions during the different stages of the JKube processes.

The project is divided into two modules:

• jkube-plugin
• app

Let's start by analyzing the jkube-plugin module.

A simple JKube Plugin that generates a build timestamp file that can be used as a version, and downloads the latest version of the Spring Boot documentation in PDF.

The plugin contains just a class implementing the JKubePlugin interface, and a resource file with its declaration so that it can be automatically injected and used by Eclipse JKube.

The files generated by this plugin are then consumed by the app module. Let's analyze it.

This module contains a very simple Spring Boot application that exposes 2 endpoints that can be consumed through a web browser.

The first endpoint /version returns the contents of the file containing the build timestamp that was generated by the custom plugin.

The second endpoint / is the home landing page of the web application. It will automatically load and present the latest version of the Spring Boot documentation in PDF, that was downloaded by the custom plugin.

Note how the plugin module is declared as a Kubernetes Maven Plugin dependency:

<plugin>
  <groupId>org.eclipse.jkube</groupId>
  <artifactId>kubernetes-maven-plugin</artifactId>
  <version>${jkube.version}</version>
  <dependencies>
    <dependency>
      <groupId>${project.groupId}</groupId>
      <artifactId>jkube-plugin</artifactId>
      <version>${project.version}</version>
    </dependency>
  </dependencies>
</plugin>

The Dockerfile is tuned to copy the generated and downloaded files to the container image so that they can be consumed by the application.

COPY maven/target/classes/jkube-extra/* files/

The application will attempt to load these files:

@GetMapping("/version")
public String version() throws IOException {
  if (isProd()) {
    return Files.readString(Path.of("/deployments", "files", "build-timestamp"));
  }
  return Instant.now().toString();
}

If you have Minikube, it's as simple as running the following commands from the main quickstart project directory:

eval $(minikube docker-env)
mvn clean install

Since JKube's Maven goals are bound to the install phase, this should automatically deploy the application on Minikube. You only need to run minikube service app from the command line, and a web browser window will open showing the latest Spring Boot Reference Documentation in PDF.