Docker Improvements (#32)

* Build the application using the maven docker image (no longer need to compile the app locally).

Use the Amazon Corretto JDK distro for the JRE source.  (OpenJDK has been deprecated).  Create the small JRE using the jlink tool.

Using the alpine distro as base; copy the generated JRE; copy the built application.

* Add dockerignore and fix volume

.dockerignore

@@ -0,0 +1,8 @@
+README.md
+LICENSE
+target
+docker-compose.yml
+Jenkinsfile
+Dockerfile
+mvnw
+mvnw.cmd

Dockerfile

@@ -1,11 +1,39 @@
-FROM openjdk:21-jdk-slim
+# Build the application using the maven image
+FROM maven:3.9.9 AS builder
+
+WORKDIR /build
+COPY . .
+RUN mvn clean package
+
+# Create a slimmed version of the Java JRE using the Corretto image
+FROM amazoncorretto:21.0.6-alpine AS corretto-jdk
+
+RUN apk add --no-cache binutils
+# Build small JRE image
+RUN $JAVA_HOME/bin/jlink \
+         --verbose \
+         --add-modules ALL-MODULE-PATH \
+         --strip-debug \
+         --no-man-pages \
+         --no-header-files \
+         --compress=zip-4 \
+         --output /slim_jre
+
+# Use a small Linux distro for final image
+FROM alpine:latest
+ENV JAVA_HOME=/jre
+ENV PATH="${JAVA_HOME}/bin:${PATH}"
+
+# Copy the JRE into Alpine image
+COPY --from=corretto-jdk /slim_jre $JAVA_HOME
+
+# Copy the compiled app into Alpine image
+COPY --from=builder build/target/quickdrop-0.0.1-SNAPSHOT.jar app/quickdrop.jar
 
 WORKDIR /app
 
-COPY target/quickdrop-0.0.1-SNAPSHOT.jar /app/quickdrop.jar
-
-VOLUME ["/app/db", "/app/log", "/files"]
+VOLUME ["/app/db", "/app/log", "/app/files"]
 
 EXPOSE 8080
 
-ENTRYPOINT ["java", "-jar", "/app/quickdrop.jar"]
+ENTRYPOINT ["java", "-jar", "/app/quickdrop.jar"]