documented dockerfile

Author: aballaci

Dockerfile

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+FROM maven:3.6.3-jdk-11 as MAVEN_BUILD
+
+MAINTAINER Armand Ballaci
+
+COPY pom.xml .
+
+COPY src src
+
+RUN mvn dependency:go-offline -B
+
+RUN mvn clean package -DskipTests
+
+RUN mkdir -p target/dependency && (cd target/dependency; jar -xf ../*.jar)
+
+# Production Stage for Spring boot application image
+# Also, there is a clean separation between dependencies and application resources in a Spring Boot fat jar file,
+# and we can use that fact to improve performance. The key is to create layers in the container filesystem.
+# The layers are cached both at build time and at runtime (in most runtimes) so we want the most frequently changing resources,
+# usually the class and static resources in the application itself, to be layered after the more slowly changing resources.
+# Thus we will use a slightly different implementation of the Dockerfile: https://spring.io/guides/gs/spring-boot-docker/
+FROM openjdk:11-jdk-slim as production
+ARG DEPENDENCY=target/dependency
+COPY --from=MAVEN_BUILD ${DEPENDENCY}/BOOT-INF/lib /app/lib
+COPY --from=MAVEN_BUILD ${DEPENDENCY}/META-INF /app/META-INF
+COPY --from=MAVEN_BUILD ${DEPENDENCY}/BOOT-INF/classes /app
+EXPOSE 8080
+ENTRYPOINT ["java","-cp","app:app/lib/*","de.ballaci.jpa.SakilaApplication"]