Containerizing SpringBoot Application With Jib

In this article, we will learn how to create Docker or OCI complaint images without installing a Docker client or using Dockerfile for our SpringBoot application. We will be doing all of this with the help of Jib.

What Is Jib?

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

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

Wow, this is really powerful! But how?

How to Jib

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

We will be using Spring Initializr to generate a working Spring Boot project. The source code for our Spring Boot application is available here. It just prints a Hello message when the image is pushed via Jib and the image is run through Docker.

Once we are set up ready with an 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 into your pom.xml plugin section and you are good to go. But I will try to explain the <from> and <image> tags here.

<from> configures the base image on which to build your application.

Typically, you don’t need to provide <from> as by default, as it uses a distro-less Java 8 image. However, I have used Java 11, so I have explicitly mentioned that here. Moreover, depending on 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 a Docker registry, but you can use any cloud provider's (ECS, GCR, ACR) container registry.

For other options available for use with the plugin, you can refer to the documentation.

Setting Credentials for Registry

To push an image, we will need to add registry credentials to the Maven settings.xml file. Since we are just doing a demo, it’s okay to provide credentials this way, but avoid using it in real-world projects as it is not secure. You may want to secure credentials as mentioned here.

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<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.

With an IDE

For example, in IntelliJ, you can go to the 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 that can run Maven goals like clean, compile, etc., then push your image.

Using the Command Line

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

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mvn compile jib:build

This will compile, build, and then push your application's image to the configured container registry.

The following is the output:

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ashish@MacBook-Air springboot % mvn compile jib:build

[INFO] Scanning for projects…

[INFO]

[INFO] — — — — — — — — — — < com.example:spring-boot-jib > — — — — — — — — — — -

[INFO] Building springboot 0.0.1-SNAPSHOT

[INFO] — — — — — — — — — — — — — — — — [ jar ] — — — — — — — — — — — — — — — — -

[INFO]

[INFO] — — maven-resources-plugin:3.1.0:resources (default-resources) @ spring-boot-jib — -

[INFO] Using ‘UTF-8’ encoding to copy filtered resources.

[INFO] Copying 1 resource

[INFO] Copying 0 resource

[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-image

[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] — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — —

Running an 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.

As you can see, our application is running inside a container. Now just run the curl command and you will get a hello message from our Spring Boot application.

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, but that’s not the X factor. Other benefits of using Jib for your Java applications include super easy integrating with Java applications, faster builds, reproducible builds, it's backed by Google, and more. You can go to this link to learn more about Jib's benefits in detail.

Further Reading 

You can also read some of my previous articles here.