Packaging and Running

java -jar and beyond

The Spring Boot Maven or Gradle plugin builds an executable jar containing the app and its dependencies, run with java -jar. For containers, mvn spring-boot:build-image creates an OCI image using Cloud Native Buildpacks, or you can write a Dockerfile using the layered jar for efficient caching. GraalVM native images start in milliseconds with low memory, at the cost of longer builds and some reflection constraints. Give the JVM sensible memory limits in containers.

Build and run commands

mvn package and java -jar were run for this course; the other commands need Docker or GraalVM and were not run.

mvn package                                   # builds target/shop-0.0.1-SNAPSHOT.jar (run)
java -jar target/shop-0.0.1-SNAPSHOT.jar      # starts the embedded server (run)
mvn spring-boot:build-image                   # OCI image via buildpacks (not run)
mvn -Pnative native:compile                   # GraalVM native executable (not run)

Use layered jars in Dockerfiles

Copying dependencies and application classes as separate layers makes image rebuilds much faster.

Quick check: What does a Spring Boot executable jar contain?

• A database dump
• Only your source code
• Only configuration files
• The application plus its dependencies and an embedded server