Introduction
Choosing the right Java Development Kit (JDK) base image for your containerized Java applications can impact stability, performance, and licensing. In this article, we compare OpenJDK, Zulu, and Eclipse Temurin images.
Why the JDK Image Matters
The JDK image you use as a base in your Dockerfile can affect:
- Application compatibility
- Startup time and memory usage
- Patch availability and update cadence
- Security and vendor support
Overview of Options
1. OpenJDK
The OpenJDK project provides the reference implementation of Java. It’s available as an official Docker image:
FROM openjdk:17-jdk-slim
Pros:
- Maintained by the official project
- Good default for most use cases
Cons:
- May lag behind in updates compared to vendor distributions
2. Zulu (by Azul)
Zulu is a certified build of OpenJDK by Azul, available on Docker Hub:
FROM azul/zulu-openjdk:17
Pros:
- Certified builds (TCK-tested)
- Free and open source
- Enterprise support available
Cons:
- Slightly larger images
3. Eclipse Temurin (by Adoptium)
Temurin is the successor of AdoptOpenJDK and is maintained by the Eclipse Foundation:
FROM eclipse-temurin:17-jdk
Pros:
- TCK-compliant builds
- Regular updates and security fixes
Cons:
- Image variants can be confusing
Comparison Table
| Feature | OpenJDK | Zulu | Temurin |
|---|---|---|---|
| TCK Certified | ✅ | ✅ | ✅ |
| Slim Images | ✅ | ⚠️ | ✅ |
| Update Cadence | Moderate | Frequent | Frequent |
| Support | Community | Enterprise | Community |
Recommendation
- For most developers: Temurin is a reliable, community-supported choice with good update cadence.
- For enterprise environments: Zulu offers certified builds and commercial support.
- For minimal images: stick to OpenJDK slim if you want basic functionality with low image size.
Bonus: Minimal Base Example
FROM eclipse-temurin:17-jdk-alpine
COPY . /app
WORKDIR /app
CMD ["java", "-jar", "myapp.jar"]
Conclusion
Choose the JDK base image based on your performance, support, and compatibility requirements. Test and monitor your containers to ensure the image you choose meets your operational needs.