Containerizing Spring Boot Application with Jib

In this article, we will learn about how to create docker or OCI complaint images without installing any docker client or using Dockerfile for our Spring Boot application. We will be doing all of this with help of Jib.

What is Jib?

Jib is Java containerizer from Google that lets Java developers build containers using the build tools like Maven, Gradle etc.

Jib(Image source)

But that’s not all what is really interesting about Jib is the fact that you don’t need to know anything about installing docker, maintaining Dockerfile, etc. As a developer, you only care about the artifact(jar, war, etc.) you are going to produce and you don’t have to deal with any of the docker nonsense(build/push, etc.).

Jib v/s Docker build flow(Image source Google Cloud)

Wow, this is really powerful!!! But how?

How to Jib?

With Jib you can containerize your Java applications in no time just by adding Maven or Gradle plugin to your pom.xml.or build.gradle file. It is that simple. We will be covering Maven first and in later post Gradle. Let’s get started then.

We will be using spring initializr to generate a working spring-boot project. Source code of our SpringBoot application is available here and it just prints a Hello message when the image pushed via Jib and the image is run through docker.

Once we have the setup ready with IDE we can proceed with the next step.

Setting up Maven

<plugin>
   <groupId>com.google.cloud.tools</groupId>
   <artifactId>jib-maven-plugin</artifactId>
   <version>2.6.0</version>
   <configuration>
      <from>
         <image>gcr.io/distroless/java:11</image>
      </from>
      <to>
         <image>registry.hub.docker.com/hiashish/spring-boot-jib-image</image>
      </to>
   </configuration>
</plugin>

For maven, you can paste the above content in your pom.xml plugin section and you are good to go. But I will try to explain <from> and <image> tags here.

<from> Configures the base image to build your application on top of.

Typically you don’t need to provide <from> as by default it uses distroless java8 image. However, I have used java11 so I have explicitly mentioned that here. Moreover depending upon your use case you may want to use a different base image.

<image > This refers to the target image that will pushed to the container registry.

I have used the docker registry but you can use any of the cloud provider(ECS, GCR, ACR) container registries available.

To use further options with the plugin you can refer to the documentation.

Setting credentials for registry

In order to push an image, we would need to add registry credentials to maven settings.xml. Since we are just doing a demo it’s ok to provide credentials this way but avoid using this approach as it is not secure at all. You may want to secure credentials as mentioned here.

<server>
    <id>registry.hub.docker.com</id>
    <username>username</username>
    <password>password</password>
</server>

Building an image

To build an image we can do it in the following ways.

1. IDE

For example, in IntelliJ, you can just go to maven view of your project then go under Plugins>jib then right click and run the maven build. You may want to create an IntelliJ run configuration for this which can run maven goals like clean, compile, etc. then push your image.

Run Through IntelliJ

2. Using the command line

Just run the below command to build an image of your application. Make sure you have maven installed.

mvn compile jib:build

It will compile, build, and then push the image of your application to the configured container registry.

Following is the output.

ashish@MacBook-Air springboot % mvn compile jib:build
[INFO] Scanning for projects…
[INFO]
………..
[INFO] — — maven-compiler-plugin:3.8.1:compile (default-compile) @ spring-boot-jib — -
[INFO] Nothing to compile — all classes are up to date
[INFO]
[INFO] — — jib-maven-plugin:2.6.0:build (default-cli) @ spring-boot-jib — -
[WARNING] ‘mainClass’ configured in ‘maven-jar-plugin’ is not a valid Java class: ${start-class}
[INFO]
[INFO] Containerizing application to registry.hub.docker.com/hiashish/spring-boot-jib-image…
[WARNING] Base image ‘gcr.io/distroless/java:11’ does not use a specific image digest — build may not be reproducible
[INFO] Using credentials from Maven settings file for registry.hub.docker.com/hiashish/spring-boot-jib-imge
[INFO] Using base image with digest: sha256:b25c7a4f771209c2899b6c8a24fda89612b5e55200ab14aa10428f60fd5ef1d1
[INFO]
[INFO] Executing tasks:
[INFO]
[INFO] Executing tasks:
[INFO]
[INFO] Executing tasks:
[INFO] [======= ] 25.0% complete
[INFO]
[INFO] Executing tasks:
[INFO] [======= ] 25.0% complete
[INFO] > pushing blob sha256:6508f436f385b3751366f90b6…
[INFO]
[INFO] Executing tasks:
[INFO] [======= ] 25.0% complete
[INFO] > pushing blob sha256:6508f436f385b3751366f90b6…
[INFO] > pushing blob sha256:c5e22041fc97b838b93a2e18d…
[INFO]
[INFO] Executing tasks:
[INFO] [======= ] 25.0% complete
[INFO] > pushing blob sha256:6508f436f385b3751366f90b6…
[INFO] > pushing blob sha256:c5e22041fc97b838b93a2e18d…
[INFO] > pushing blob sha256:b25902383f9ee26808b68ca62…
[INFO]
[INFO] Executing tasks:
[INFO] [======= ] 25.0% complete
[INFO] > pushing blob sha256:6508f436f385b3751366f90b6…
[INFO] > pushing blob sha256:c5e22041fc97b838b93a2e18d…
[INFO] > pushing blob sha256:b25902383f9ee26808b68ca62…
[INFO] > checking base image layer sha256:31eb28996804…
[INFO]
[INFO] Executing tasks:
[INFO] [======== ] 27.8% complete
[INFO] > pushing blob sha256:c5e22041fc97b838b93a2e18d…
[INFO] > pushing blob sha256:b25902383f9ee26808b68ca62…
[INFO] > checking base image layer sha256:31eb28996804…
[INFO]
[INFO] Executing tasks:
[INFO] [========= ] 30.6% complete
[INFO] > pushing blob sha256:c5e22041fc97b838b93a2e18d…
[INFO] > checking base image layer sha256:31eb28996804…
[INFO]
[INFO] Executing tasks:
[INFO] [========== ] 33.3% complete
[INFO] > checking base image layer sha256:31eb28996804…
[INFO]
[INFO] Executing tasks:
[INFO] [=========== ] 35.0% complete
[INFO]
[INFO] Executing tasks:
[INFO]
[INFO]
[INFO]
[INFO] Container entrypoint set to [java, -cp, /app/resources:/app/classes:/app/libs/*, com.jib.example.spring.SpringbootApplication]
[INFO]
[INFO] Built and pushed image as registry.hub.docker.com/hiashish/spring-boot-jib-image
[INFO] Executing tasks:
[INFO] [=========================== ] 91.7% complete
[INFO] > launching layer pushers
[INFO]
[INFO] — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — —
[INFO] BUILD SUCCESS
[INFO] — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — —
[INFO] Total time: 8.746 s
[INFO] Finished at: 2020–11–16T02:34:33+05:30
[INFO] — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — —

Run the image

We have successfully pushed the image(image name:spring-boot-jib-image) to a docker registry. Now we can run the image using docker.

Run the image

As you can see that our application is running inside a container. Now just run the curl command and you can see that we got a hello message from our spring-boot application.

Hello message

Quick Demo

Conclusion

In this article, we have learned how we can containerize our Java applications without docker. Additionally, with Jib you can build images using docker also but that’ not the X factor. Other benefits of using Jib for your Java applications include super easy to integrate, faster builds, reproducible builds, Backed by Google, etc. You can go through this link to know about Jib's benefits in detail.

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Further reading

You can also read some of my previous articles.

Running Simple Spring Boot Application on Openshift(Minishift)

CI/CD Workflow for Spring Boot Applications on Kubernetes via Skaffold