Dockerfile

# maven build
FROM maven:3.6.1-jdk-11-slim AS MAVEN_TOOL_CHAIN
COPY pom-docker.xml /tmp/pom.xml
COPY src /tmp/src/
COPY settings-docker.xml /usr/share/maven/ref/
WORKDIR /tmp/
RUN mvn -s /usr/share/maven/ref/settings-docker.xml package

# jlinked java 11 (do NOT use alpine-slim here which has important module files deleted)
FROM adoptopenjdk/openjdk11:jdk-11.0.9_11-alpine AS JLINKED_JAVA
RUN ["jlink", "--compress=2", \
     "--module-path", "/opt/java/openjdk/jmods", \
     "--add-modules", "java.base,java.compiler,java.desktop,java.instrument,java.management,java.prefs,java.rmi,java.scripting,java.security.jgss,java.security.sasl,java.sql.rowset,jdk.httpserver,jdk.jdi,jdk.unsupported", \
     "--output", "/jlinked"]

# final custom slim java image (for apk command see jdk-11.0.9_11-alpine-slim)
FROM alpine:3.12
RUN apk add --no-cache tzdata --virtual .build-deps curl binutils zstd \
    && GLIBC_VER="2.31-r0" \
    && ALPINE_GLIBC_REPO="https://github.com/sgerrand/alpine-pkg-glibc/releases/download" \
    && GCC_LIBS_URL="https://archive.archlinux.org/packages/g/gcc-libs/gcc-libs-10.1.0-2-x86_64.pkg.tar.zst" \
    && GCC_LIBS_SHA256="f80320a03ff73e82271064e4f684cd58d7dbdb07aa06a2c4eea8e0f3c507c45c" \
    && ZLIB_URL="https://archive.archlinux.org/packages/z/zlib/zlib-1%3A1.2.11-3-x86_64.pkg.tar.xz" \
    && ZLIB_SHA256=17aede0b9f8baa789c5aa3f358fbf8c68a5f1228c5e6cba1a5dd34102ef4d4e5 \
    && curl -LfsS https://alpine-pkgs.sgerrand.com/sgerrand.rsa.pub -o /etc/apk/keys/sgerrand.rsa.pub \
    && SGERRAND_RSA_SHA256="823b54589c93b02497f1ba4dc622eaef9c813e6b0f0ebbb2f771e32adf9f4ef2" \
    && echo "${SGERRAND_RSA_SHA256} */etc/apk/keys/sgerrand.rsa.pub" | sha256sum -c - \
    && curl -LfsS ${ALPINE_GLIBC_REPO}/${GLIBC_VER}/glibc-${GLIBC_VER}.apk > /tmp/glibc-${GLIBC_VER}.apk \
    && apk add --no-cache /tmp/glibc-${GLIBC_VER}.apk \
    && curl -LfsS ${ALPINE_GLIBC_REPO}/${GLIBC_VER}/glibc-bin-${GLIBC_VER}.apk > /tmp/glibc-bin-${GLIBC_VER}.apk \
    && apk add --no-cache /tmp/glibc-bin-${GLIBC_VER}.apk \
    && curl -Ls ${ALPINE_GLIBC_REPO}/${GLIBC_VER}/glibc-i18n-${GLIBC_VER}.apk > /tmp/glibc-i18n-${GLIBC_VER}.apk \
    && apk add --no-cache /tmp/glibc-i18n-${GLIBC_VER}.apk \
    && /usr/glibc-compat/bin/localedef --force --inputfile POSIX --charmap UTF-8 "$LANG" || true \
    && echo "export LANG=$LANG" > /etc/profile.d/locale.sh \
    && curl -LfsS ${GCC_LIBS_URL} -o /tmp/gcc-libs.tar.zst \
    && echo "${GCC_LIBS_SHA256} */tmp/gcc-libs.tar.zst" | sha256sum -c - \
    && mkdir /tmp/gcc \
    && zstd -d /tmp/gcc-libs.tar.zst --output-dir-flat /tmp \
    && tar -xf /tmp/gcc-libs.tar -C /tmp/gcc \
    && mv /tmp/gcc/usr/lib/libgcc* /tmp/gcc/usr/lib/libstdc++* /usr/glibc-compat/lib \
    && strip /usr/glibc-compat/lib/libgcc_s.so.* /usr/glibc-compat/lib/libstdc++.so* \
    && curl -LfsS ${ZLIB_URL} -o /tmp/libz.tar.xz \
    && echo "${ZLIB_SHA256} */tmp/libz.tar.xz" | sha256sum -c - \
    && mkdir /tmp/libz \
    && tar -xf /tmp/libz.tar.xz -C /tmp/libz \
    && mv /tmp/libz/usr/lib/libz.so* /usr/glibc-compat/lib \
    && apk del --purge .build-deps glibc-i18n \
    && rm -rf /tmp/*.apk /tmp/gcc /tmp/gcc-libs.tar* /tmp/libz /tmp/libz.tar.xz /var/cache/apk/*

ENV JAVA_VERSION jdk-11.0.9.1+1
COPY --from=JLINKED_JAVA /jlinked /opt/java/openjdk
ENV JAVA_HOME=/opt/java/openjdk \
PATH="/opt/java/openjdk/bin:$PATH"

# add spring boot application
VOLUME /tmp
COPY --from=MAVEN_TOOL_CHAIN /tmp/target/camunda-bpm-identity-keycloak-examples-sso-kubernetes*.jar ./app.jar
ENTRYPOINT ["java","-Djava.security.egd=file:/dev/./urandom","-jar","/app.jar"]