Dockerfile.03.dockercache

# ------------------------------------------------------------
# Stage: build
# Purpose: compile the application using Maven with cache mounts enabled
# Base image: maven:3.9.12-eclipse-temurin-21-noble
# Maven profile: -Pprod
# Artifact: target/hello-world-*-SNAPSHOT.jar
# Notes: uses --mount=type=cache for /root/.m2 to speed up builds; cache is not persisted in final image
# ------------------------------------------------------------
FROM maven:3.9.12-eclipse-temurin-21-noble AS stage-build

WORKDIR /app

LABEL maintainer="Emmanuel Bruno <emmanuel.bruno@univ-tln.fr>"
LABEL description="Java Hello World Application - multi-stage build"
LABEL version="0.1.0-SNAPSHOT"
LABEL license="MIT"

# Copy wrapper
COPY mvnw ./
COPY .mvn .mvn
RUN chmod +x mvnw

# Copy POM first to leverage Docker cache for dependencies
COPY pom.xml ./
RUN --mount=type=cache,target=/root/.m2 ./mvnw --batch-mode dependency:resolve

# Copy source code and build the application
COPY src ./src
RUN --mount=type=cache,target=/root/.m2 ./mvnw --batch-mode -Pprod -DskipTests clean package

# ------------------------------------------------------------
# Stage: runtime
# Purpose: minimal runtime with Temurin JRE containing the packaged application
# Base image: eclipse-temurin:21.0.9_10-jre-noble
# Copies: /app/app.jar and /app/libs from build stage
# Notes: create a non-root user for security and set JAVA_OPTS appropriately
# ------------------------------------------------------------
FROM eclipse-temurin:21.0.9_10-jre-noble

LABEL maintainer="Emmanuel Bruno <emmanuel.bruno@univ-tln.fr>"
LABEL description="Java Hello World Application - multi-stage runtime"

WORKDIR /app

# Copy only the built jar from the build stage
COPY --from=stage-build /app/target/hello-world-*-SNAPSHOT.jar /app/app.jar
# Copy the libs directory (containing dependencies) if needed
COPY --from=stage-build /app/target/libs /app/libs

# Create a non-root user for security and ensure app files are owned by that user
RUN groupadd -r appuser && useradd -r -u 1001 -g appuser -m appuser \
    && chown -R appuser:appuser /app

USER appuser
ENV HOME=/home/appuser

# Configure Java options for container environment
ENV JAVA_OPTS="-XX:+UseContainerSupport -XX:MaxRAMPercentage=75.0"
# Install generic entrypoint script
COPY entrypoint.sh /usr/local/bin/entrypoint.sh
RUN chmod +x /usr/local/bin/entrypoint.sh || true

# Use generic exec-form entrypoint
ENTRYPOINT ["/usr/local/bin/entrypoint.sh"]