docker.txt

# syntax=docker/dockerfile:1

# Create a stage for resolving and downloading dependencies.
FROM openjdk:8u181-jdk-slim as deps

WORKDIR /build

# Copy the mvnw wrapper with executable permissions.
COPY --chmod=0755 mvnw mvnw
COPY mvnw.cmd mvnw.cmd
COPY .mvn/ .mvn/
COPY pom.xml .

# Download dependencies as a separate step to take advantage of Docker's caching.
# Leverage a cache mount to /root/.m2 so that subsequent builds don't have to re-download packages.
RUN --mount=type=cache,target=/root/.m2 ./mvnw dependency:go-offline -DskipTests

################################################################################

# Create a stage for building the application based on the stage with downloaded dependencies.
FROM deps as package

WORKDIR /build

COPY . .
RUN --mount=type=cache,target=/root/.m2 ./mvnw package -DskipTests && \
    mv target/$(./mvnw help:evaluate -Dexpression=project.artifactId -q -DforceStdout)-$(./mvnw help:evaluate -Dexpression=project.version -q -DforceStdout).jar target/app.jar

################################################################################

# Create a new stage for running the application that contains the minimal runtime dependencies for the application.
FROM openjdk:8u181-jre-slim AS final

# Create a non-privileged user that the app will run under.
ARG UID=10001
RUN adduser --disabled-password --gecos "" --home "/nonexistent" --shell "/sbin/nologin" --no-create-home --uid "${UID}" appuser
USER appuser

# Copy the executable from the "package" stage.
COPY --from=package /build/target/app.jar app.jar

EXPOSE 8080

ENTRYPOINT [ "java", "-jar", "app.jar" ]