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Docker conventions

Consider using a linter such as hadolint.

ENV commands

Break ENV commands into one line per command. ENV no longer adds a layer in new Docker versions, so there is no need to chain them on a single line.

Labels

Use Open Containers labels, at least including

  • org.opencontainers.image.version
  • org.opencontainers.image.vendor
  • org.opencontainers.image.title
  • org.opencontainers.image.url

Multistage builds

Where applicable, use a multistage build to separate build-time and runtime, thereby keeping final images small. For example, when using Maven, Maven is only needed to assemble, not to run.

Here, maven:3-eclipse-temurin-25 is used as a base image, Maven is used to compile and build a JAR artifact, and everything but the JAR is discarded. eclipse-temurin:25 is used as the runtime base image, and only the JAR file is needed.

FROM maven:3-eclipse-temurin-25 AS build
WORKDIR /root
RUN --mount=type=cache mvn package

FROM eclipse-temurin:25 AS run
ARG JAR_FILE=target/*.jar
COPY --from=build $JAR_FILE my-app.jar
EXPOSE 443
ENTRYPOINT java -jar my-app.jar