This is an update to the original blog post about  creating docker images with Spring Boot 2.3.

There were a few things related to image creation that changed between the first milestone of Spring Boot 2.3 and the GA release.

The two new features introduced in Spring Boot 2.3 to help improve image creation techniques were: layered jars and buildpack support.

Layered Jars

The layered jar feature evolved quite a bit as we started adding support for custom layers. While the need to express layers that the jar should be split into for image creation was evident, changing the format of the jar to do so no longer seemed necessary.

Spring Boot 2.3 includes support for layering a jar using a layers.idx file. The layers index file provides a list of layers and the parts of the jar that should be contained within them. Layers are written in the order that they should be added to the Docker/OCI image.

By default, the following layers are defined:

• dependencies for any dependency whose version does not contain SNAPSHOT.
• spring-boot-loader for the jar loader classes.
• snapshot-dependencies for any dependency whose version contains SNAPSHOT.
• application for application classes and resources.

#docker #spring boot 2.3 #spring boot