How to reduce image size of Java App

The simplest Dockerfile

let's build our Dockerfile image and compare the sizes of our JAR file and the created Docker image.

If we look at the SIZE column, we can see that the size of our Docker image is 465MB!

How to know each layer size

To do this, we will use a tool called Dive which is used for exploring a docker image, layer contents, and discovering ways to shrink the size of your Docker/OCI image.

To install Dive, follow the guide in their README:

Customizing JRE using jlink

Let’s now build our container image and find out how much smaller it has become.

Stripping Image Size, Even More, Using jdeps

What if I told you that the size of our container image can be made even smaller? When paired with jlink, you can also use the Java Dependency Analysis Tool (jdeps), which was first introduced in Java 8, to understand the static dependencies of your applications and libraries.

The only thing left to do is to see how much the container image has shrunk using our latest Dockerfile:

References

1. https://dzone.com/articles/ways-to-reduce-jvm-docker-image-size
2. https://blog.monosoul.dev/2022/04/25/reduce-java-docker-image-size/
3. https://bell-sw.com/blog/how-to-dockerize-a-spring-boot-app-with-the-smallest-base-image/
4. https://medium.com/@ievgen.degtiarenko/reduce-size-of-docker-image-with-spring-boot-application-2b3632263350
5. https://bell-sw.com/announcements/2021/01/13/Secrets-behind-tiny-Docker-containers-for-Java-microservices/