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🐳💡 What Is Jib?

#docker #jib

Jib is a tool created by Google to help Java developers create Docker images for their applications without writing a Dockerfile and even without installing Docker locally (optional). It works only for Java applications.

Think of Jib as a shortcut that turns your Java app into a Docker image easily.

🛠 Why Use Jib Instead of Other Tools?

  • Only for Java apps (not Node.js, Python, etc.).
  • No need to write a Dockerfile.
  • Faster than Buildpacks (another tool for creating Docker images).
  • Can work without Docker installed, by pushing images directly to a remote repository (like Docker Hub).

🚀 Steps to Use Jib with Maven

Let’s say you want to containerize a Java microservice named cards using Maven.

1. 📦 Go to Jib GitHub

Link: https://github.com/GoogleContainerTools/jib

There you’ll find guides on how to use Jib with Maven or Gradle.

Since you're using Maven, follow the Maven instructions.

2. 🧩 Add Jib Plugin to pom.xml

Open your cards service’s pom.xml file and add the following plugin:

<build>
  <plugins>
    <!-- existing plugins like spring-boot-maven-plugin -->

    <plugin>
      <groupId>com.google.cloud.tools</groupId>
      <artifactId>jib-maven-plugin</artifactId>
      <version>3.3.2</version>
      <configuration>
        <to>
          <image>your-dockerhub-username/cards:S4</image>
        </to>
      </configuration>
    </plugin>
  </plugins>
</build>
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Make sure to:

  • Replace your-dockerhub-username with your actual Docker Hub username.
  • Ensure packaging is set to jar.

3. 🧹 Clean Project

Before building, clean the previous builds:

mvn clean
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4. 🔧 Build Docker Image Using Jib

Now, generate the Docker image:

mvn compile jib:dockerBuild
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This will create a Docker image using your local Docker (no need for a Dockerfile).

✅ If successful, it will build the image very quickly (in the demo: ~11 seconds).

5. 🐋 Check Docker Image

Run:

docker images
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You’ll see the cards image listed there.

6. ▶️ Run the Docker Container

Now run your container:

docker run -d -p 9000:9000 your-dockerhub-username/cards:S4
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  • -d means run in background.
  • -p 9000:9000 means map local port 9000 to container port 9000.

7. 📬 Test the API

Use Postman or browser to test if the service is running:

http://localhost:9000/api/create
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✅ If you get a response, everything is working fine!

❓Why the "43 Years Ago" Timestamp?

You might see that the Docker image says it was created "43 years ago".

  • This is NOT a bug!
  • It’s a feature to optimize caching. If nothing changes, the image content and date stay the same, which makes builds faster and more efficient.

💻 What If You Don’t Have Docker Installed?

You can still build the Docker image and push it to a remote registry (like Docker Hub) directly.

Run this command instead:

mvn compile jib:build
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This will push the image to Docker Hub (or GCR/ECR) instead of building it locally. Just make sure your image name is correct and you are logged in.

✅ Summary

Step What You Do
1️⃣ Add Jib plugin to pom.xml
2️⃣ Clean your project
3️⃣ Run mvn compile jib:dockerBuild
4️⃣ Check the image with docker images
5️⃣ Run it with docker run
6️⃣ Test it using Postman
🧠 Remember: No Dockerfile needed!

🆚 Jib vs Buildpacks

Feature Jib Buildpacks
Language Support Only Java Java, Python, Node, etc.
Dockerfile Required ❌ No ❌ No
Fast Build ✅ Yes ❌ Slower
No Docker Needed ✅ Yes (optional) ❌ No

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