Dockerfile

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# ---------- 1️⃣  BUILD STAGE --------------------------------------------------
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# • Uses the official Eclipse-Temurin image that bundles Maven3+jdk17
# • Build steps are cached layer‑by‑layer to speed up “docker build” in CI as
#   well as on your laptop (requires BuildKit, which is on by default in Docker
#   Desktop and recent Docker engines).

FROM maven:3.9.6-eclipse-temurin-17 AS build

# Use an unprivileged user inside the builder for a tiny security boost
RUN useradd -ms /bin/bash builder
USER builder

WORKDIR /src

# -- 1. Copy only the pom.xml first and go offline.  This creates a cache layer
#       containing your dependencies so the costly "mvn dependency:go‑offline"
#       runs only when pom.xml changes.
COPY --chown=builder:builder pom.xml .
RUN mvn -q dependency:go-offline

# -- 2. Now copy the actual source code
COPY --chown=builder:builder src ./src

# -- 3. Compile and package.  -DskipTests is common in container builds;
#       run tests in a separate CI step if you need them.
RUN mvn -q package -DskipTests

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# ---------- 2️⃣  RUNTIME STAGE -----------------------------------------------
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# • This layer contains nothing except the JAR and a JRE.
# • The resulting image is ~65MB on amd64 / arm64.

FROM eclipse-temurin:23-jre
WORKDIR /app

# Copy the shaded / normal jar produced by the build stage
# (the wildcard picks up whatever version number Maven generates).
COPY --from=build /src/target/vertx-proxy-1.0-SNAPSHOT.jar proxy.jar

# Basically a note - the image exposes this port
EXPOSE 4000

# Launch the proxy
ENTRYPOINT ["sh", "-c", "exec java -jar proxy.jar"]