TopolearnYou need a fast dev loop and a deployable artifact.
The Spring Boot build plugin does two jobs. During development, ./mvnw spring-boot:run (or ./gradlew bootRun) starts the app from source. For deployment, ./mvnw package (or ./gradlew bootJar) produces an executable fat jar in target/ that contains your classes, all dependency jars and a small launcher, runnable anywhere with a JVM: java -jar target/shop-0.0.1-SNAPSHOT.jar.
Use the wrapper scripts (mvnw, gradlew) that Initializr generates, so everyone builds with the same tool version.
DevTools (spring-boot-devtools, a development-only dependency) restarts the application automatically when classes change on the classpath, which is much faster than a cold start, and disables template caching. It is excluded from packaged jars automatically.
For containers, ./mvnw spring-boot:build-image builds an OCI image with Cloud Native Buildpacks, no Dockerfile required. If you write your own Dockerfile, extract the jar into layers (java -Djarmode=tools -jar app.jar extract --layers) so dependency layers are cached between builds.
At startup the log shows the active profiles, the port and the startup time, and --debug prints the auto-configuration report, useful when something isn't configured the way you expect.
Example
# development
./mvnw spring-boot:run # or: ./gradlew bootRun
# package an executable jar and run it
./mvnw clean package
java -jar target/shop-0.0.1-SNAPSHOT.jar --server.port=9090
# container image via buildpacks (needs Docker)
./mvnw spring-boot:build-image -Dspring-boot.build-image.imageName=shop:latest
docker run -p 8080:8080 shop:latest
# see why things were (not) auto-configured
java -jar target/shop-0.0.1-SNAPSHOT.jar --debug | grep -A3 "Positive matches"Remember
spring-boot:run/bootRunfor development,package/bootJarfor a fat jar- The fat jar runs anywhere with
java -jar - DevTools restarts on change and is dropped from production jars
build-imagecreates a container image without a Dockerfile
Watch out for
- Deploying the plain (non-repackaged) jar, which lacks dependencies and fails with ClassNotFoundException.