Dockerfiles

虽然只需在 Dockerfile 中使用几行代码就可以将 Spring Boot uber jar 转换为 Docker 镜像，但使用 分层功能 将产生一个优化的镜像。 当您创建一个包含层索引文件的 jar 时，spring-boot-jarmode-tools jar 将作为依赖项添加到您的 jar 中。 有了这个 jar 在类路径上，您可以在特殊模式下启动应用程序，这允许引导代码运行与您的应用程序完全不同的内容，例如，提取层的内容。

tools 模式不能与包含启动脚本的 完全可执行的 Spring Boot 归档文件 一起使用。 在构建打算与 extract tools 模式命令一起使用的 jar 文件时，请禁用启动脚本配置。

以下是如何使用 tools jar 模式启动您的 jar：

$ java -Djarmode=tools -jar my-app.jar

这将提供以下输出：

Usage:
  java -Djarmode=tools -jar my-app.jar

Available commands:
  extract      Extract the contents from the jar
  list-layers  List layers from the jar that can be extracted
  help         Help about any command

extract 命令可用于轻松地将应用程序拆分为要添加到 Dockerfile 的层。 以下是使用 jarmode 的 Dockerfile 示例。

# Perform the extraction in a separate builder container
FROM bellsoft/liberica-openjre-debian:24-cds AS builder
WORKDIR /builder
# This points to the built jar file in the target folder
# Adjust this to 'build/libs/*.jar' if you're using Gradle
ARG JAR_FILE=target/*.jar
# Copy the jar file to the working directory and rename it to application.jar
COPY ${JAR_FILE} application.jar
# Extract the jar file using an efficient layout
RUN java -Djarmode=tools -jar application.jar extract --layers --destination extracted

# This is the runtime container
FROM bellsoft/liberica-openjre-debian:24-cds
WORKDIR /application
# Copy the extracted jar contents from the builder container into the working directory in the runtime container
# Every copy step creates a new docker layer
# This allows docker to only pull the changes it really needs
COPY --from=builder /builder/extracted/dependencies/ ./
COPY --from=builder /builder/extracted/spring-boot-loader/ ./
COPY --from=builder /builder/extracted/snapshot-dependencies/ ./
COPY --from=builder /builder/extracted/application/ ./
# Start the application jar - this is not the uber jar used by the builder
# This jar only contains application code and references to the extracted jar files
# This layout is efficient to start up and CDS/AOT cache friendly
ENTRYPOINT ["java", "-jar", "application.jar"]

假设上述 Dockerfile 在当前目录中，您可以使用 docker build . 构建 Docker 镜像，或者可选地指定应用程序 jar 的路径，如下例所示：

$ docker build --build-arg JAR_FILE=path/to/myapp.jar .

这是一个多阶段 Dockerfile。 构建器阶段提取稍后需要的目录。 每个 COPY 命令都与 jarmode 提取的层相关。

当然，Dockerfile 也可以不使用 jarmode 编写。 您可以使用 unzip 和 mv 的组合将内容移动到正确的层，但 jarmode 简化了这个过程。 此外，jarmode 创建的布局默认就是 CDS 和 AOT 缓存友好的。

CDS

如果您想额外启用 CDS，您可以使用这个 Dockerfile：

# Perform the extraction in a separate builder container
FROM bellsoft/liberica-openjre-debian:24-cds AS builder
WORKDIR /builder
# This points to the built jar file in the target folder
# Adjust this to 'build/libs/*.jar' if you're using Gradle
ARG JAR_FILE=target/*.jar
# Copy the jar file to the working directory and rename it to application.jar
COPY ${JAR_FILE} application.jar
# Extract the jar file using an efficient layout
RUN java -Djarmode=tools -jar application.jar extract --layers --destination extracted

# This is the runtime container
FROM bellsoft/liberica-openjre-debian:24-cds
WORKDIR /application
# Copy the extracted jar contents from the builder container into the working directory in the runtime container
# Every copy step creates a new docker layer
# This allows docker to only pull the changes it really needs
COPY --from=builder /builder/extracted/dependencies/ ./
COPY --from=builder /builder/extracted/spring-boot-loader/ ./
COPY --from=builder /builder/extracted/snapshot-dependencies/ ./
COPY --from=builder /builder/extracted/application/ ./
# Execute the CDS training run
RUN java -XX:ArchiveClassesAtExit=application.jsa -Dspring.context.exit=onRefresh -jar application.jar
# Start the application jar with CDS enabled - this is not the uber jar used by the builder
# This jar only contains application code and references to the extracted jar files
# This layout is efficient to start up and CDS friendly
ENTRYPOINT ["java", "-XX:SharedArchiveFile=application.jsa", "-jar", "application.jar"]

这与上面的 Dockerfile 基本相同。 作为最后步骤，它通过执行训练运行来创建 CDS 归档，并将 CDS 参数传递给 java -jar。

AOT cache

如果您想额外启用 AOT cache，您可以使用这个 Dockerfile：

# Perform the extraction in a separate builder container
FROM bellsoft/liberica-openjre-debian:24-cds AS builder
WORKDIR /builder
# This points to the built jar file in the target folder
# Adjust this to 'build/libs/*.jar' if you're using Gradle
ARG JAR_FILE=target/*.jar
# Copy the jar file to the working directory and rename it to application.jar
COPY ${JAR_FILE} application.jar
# Extract the jar file using an efficient layout
RUN java -Djarmode=tools -jar application.jar extract --layers --destination extracted

# This is the runtime container
FROM bellsoft/liberica-openjre-debian:24-cds
WORKDIR /application
# Copy the extracted jar contents from the builder container into the working directory in the runtime container
# Every copy step creates a new docker layer
# This allows docker to only pull the changes it really needs
COPY --from=builder /builder/extracted/dependencies/ ./
COPY --from=builder /builder/extracted/spring-boot-loader/ ./
COPY --from=builder /builder/extracted/snapshot-dependencies/ ./
COPY --from=builder /builder/extracted/application/ ./
# Execute the AOT cache training run
RUN java -XX:AOTMode=record -XX:AOTConfiguration=app.aotconf -Dspring.context.exit=onRefresh -jar application.jar
RUN java -XX:AOTMode=create -XX:AOTConfiguration=app.aotconf -XX:AOTCache=app.aot -jar application.jar && rm app.aotconf
# Start the application jar with AOT cache enabled - this is not the uber jar used by the builder
# This jar only contains application code and references to the extracted jar files
# This layout is efficient to start up and AOT cache friendly
ENTRYPOINT ["java", "-XX:AOTCache=app.aot", "-jar", "application.jar"]

这与上面的 Dockerfile 基本相同。 作为最后步骤，它通过执行训练运行来创建 AOT 缓存文件，并将 AOT 缓存参数传递给 java -jar。