Deployment

A Spring Boot application is packaged as a single executable jar that includes its web server. You can run that jar directly on a server, or build a container image and deploy it to a platform such as Kubernetes. This chapter covers packaging, container images, production configuration and Actuator health checks.

Build an executable jar

# Gradle: build/libs/demo-0.0.1-SNAPSHOT.jar
./gradlew bootJar

# Maven: target/demo-0.0.1-SNAPSHOT.jar
./mvnw package

java -jar build/libs/demo-0.0.1-SNAPSHOT.jar

Gradle's build task also produces a -plain.jar without dependencies; deploy the jar without plain in its name. The target machine needs only a JRE.

Passing production configuration

Treat the configuration inside the jar as defaults and pass environment-specific values at launch through environment variables or command-line arguments. Never bake secrets into images or commit them to the repository.

export SPRING_PROFILES_ACTIVE=prod
export SPRING_DATASOURCE_URL=jdbc:postgresql://db:5432/demo
export SPRING_DATASOURCE_PASSWORD=change-me
java -jar demo.jar --server.port=8080

Container images with Buildpacks

You can build an image without writing a Dockerfile, using Cloud Native Buildpacks. Docker must be running; the buildpack chooses the JRE, splits the image into layers and tunes memory settings for you.

./gradlew bootBuildImage --imageName=myorg/demo
./mvnw spring-boot:build-image -Dspring-boot.build-image.imageName=myorg/demo

docker run -p 8080:8080 myorg/demo

Container images with a Dockerfile

If you want full control over the image, write a Dockerfile. Extracting the jar into layers means a code-only change does not invalidate the dependency layers, which makes rebuilds and pulls faster.

FROM eclipse-temurin:21-jre AS builder
WORKDIR /builder
COPY build/libs/demo-0.0.1-SNAPSHOT.jar application.jar
RUN java -Djarmode=tools -jar application.jar extract --layers --destination extracted

FROM eclipse-temurin:21-jre
WORKDIR /application
COPY --from=builder /builder/extracted/dependencies/ ./
COPY --from=builder /builder/extracted/spring-boot-loader/ ./
COPY --from=builder /builder/extracted/snapshot-dependencies/ ./
COPY --from=builder /builder/extracted/application/ ./
ENTRYPOINT ["java", "-jar", "application.jar"]

Health checks with Actuator

spring-boot-starter-actuator adds production endpoints. Only /actuator/health is exposed over HTTP by default; expose others selectively.

management:
  endpoints:
    web:
      exposure:
        include: health,info
  endpoint:
    health:
      probes:
        enabled: true
      show-details: when-authorized