Initial docker image is added

Author: Nasruddin

README.md

@@ -1,2 +1,4 @@
 # spring-boot-based-microservices
 WIP revamping existing codebase to support new features
+
+## 1. Docker file - upgrade to java 17 slim image once available

microservices/course-composite-service/Dockerfile

@@ -0,0 +1,17 @@
+# stage 1
+# Start with a base image containing Java runtime
+# TODO :: Upgrade to slim jre version for 17 once available
+FROM openjdk:17-alpine as builder
+WORKDIR application
+ARG JAR_FILE=target/*.jar
+COPY ${JAR_FILE} application.jar
+RUN java -Djarmode=layertools -jar application.jar extract
+
+# the second stage of our build will copy the extracted layers
+FROM openjdk:17-alpine
+WORKDIR application
+COPY --from=builder application/dependencies/ ./
+COPY --from=builder application/spring-boot-loader/ ./
+COPY --from=builder application/snapshot-dependencies/ ./
+COPY --from=builder application/application/ ./
+ENTRYPOINT ["java", "org.springframework.boot.loader.JarLauncher"]