Class Data Sharing

Spring Boot’s support for Cloud Native Buildpacks along with the Paketo Java buildpack and its Spring Boot support can be used to generate a Docker image containing a CDS-optimized application.

To enable CDS optimization in a generated Docker image, the buildpack environment variable BP_JVM_CDS_ENABLED should be set to true when building the image as described in the Maven plugin and Gradle plugin documentation. This will cause the buildpack to do a training run of the application, save the CDS archive in the image, and use the CDS archive when launching the application.

The buildpack environment variable BP_SPRING_AOT_ENABLED can also be set to true to enable AOT mode along with CDS when running an application that has been built with Ahead-of-Time processed.

The Paketo Buildpack for Spring Boot documentation has information on other configuration options that can be enabled with builder environment variables, like CDS_TRAINING_JAVA_TOOL_OPTIONS that allows to override the default JAVA_TOOL_OPTIONS, only for the CDS training run.

When performing the training run, it may be needed to customize the Spring Boot application configuration to prevent connections to remote services that may happen before the Spring lifecycle is started. This can typically happen with early database interactions and can be handled via related configuration that can be applied by default to your application (or specifically to the training run) to prevent such interactions, see related documentation.