使用Maven插件构建Spring Boot应用程序镜像

2023-08-08 23:32:16

使用Maven插件构建Spring Boot应用程序的Docker镜像。

环境准备

1.Linux系统

2.安装JDK，Maven

3.安装Docker

应用实践

1.在应用程序根目录下添加Dockerfile文件

并在Dockerfile中编辑构建内容：

FROM openjdk:8-jdk-alpine

VOLUME /tmp

ARG JAR_FILE

COPY ${JAR_FILE} app.jar

ENTRYPOINT ["java","-Djava.security.egd=file:/dev/./urandom","-jar","/app.jar"]

2.在项目pom.xml中添加docker镜像构建插件dockerfile-maven-plugin

<build>

    <plugins>

        <!-- 使用Maven插件直接将应用打包为一个Docker镜像 -->

        <plugin>

            <groupId>com.spotify</groupId>

            <artifactId>dockerfile-maven-plugin</artifactId>

            <version>1.3.6</version>

            <configuration>

                <repository>${docker.image.prefix}/${project.artifactId}</repository>

                <buildArgs>

                    <JAR_FILE>target/${project.build.finalName}.jar</JAR_FILE>

                </buildArgs>

            </configuration>

        </plugin>

    </plugins>

</build>

显然，在插件dockerfile-maven-plugin中配置了2个参数：

<repository>：指定镜像仓库信息及镜像名称，如：springio/test-springboot
<buildArgs>：设置构建参数，该参数可以直接在Dockerfile中使用（但是必须在Dockerfile使用ARG指令声明）

3.执行构建

在Spring Boot应用根目录下执行构建：

mvn install dockerfile:build

将会看到如下构建日志：

...

[INFO] Building Docker context /home/chench/workspace/java/test-springboot

[INFO]

[INFO] Image will be built as springio/test-springboot:latest

[INFO]

[INFO] Step 1/5 : FROM openjdk:8-jdk-alpine

[INFO]

[INFO] Pulling from library/openjdk

[INFO] Image ff3a5c916c92: Pulling fs layer

[INFO] Image 5de5f69f42d7: Pulling fs layer

[INFO] Image fd869c8b9b59: Pulling fs layer

[INFO] Image 5de5f69f42d7: Downloading

[INFO] Image 5de5f69f42d7: Verifying Checksum

[INFO] Image 5de5f69f42d7: Download complete

[INFO] Image ff3a5c916c92: Downloading

[INFO] Image fd869c8b9b59: Downloading

[INFO] Image ff3a5c916c92: Verifying Checksum

[INFO] Image ff3a5c916c92: Download complete

[INFO] Image ff3a5c916c92: Extracting

[INFO] Image ff3a5c916c92: Pull complete

[INFO] Image 5de5f69f42d7: Extracting

[INFO] Image 5de5f69f42d7: Pull complete

[INFO] Image fd869c8b9b59: Verifying Checksum

[INFO] Image fd869c8b9b59: Download complete

[INFO] Image fd869c8b9b59: Extracting

[INFO] Image fd869c8b9b59: Pull complete

[INFO] Digest: sha256:e82316151c501a2a0f73b3089da8dc867816470a464fcb191db9f88c2343ad53

[INFO] Status: Downloaded newer image for openjdk:8-jdk-alpine

[INFO]  ---> 224765a6bdbe

[INFO] Step 2/5 : VOLUME /tmp

[INFO]

[INFO]  ---> Running in 99fc0b2bbcf7

[INFO] Removing intermediate container 99fc0b2bbcf7

[INFO]  ---> 74c89740c46e

[INFO] Step 3/5 : ARG JAR_FILE

[INFO]

[INFO]  ---> Running in 54d9bf00c9c6

[INFO] Removing intermediate container 54d9bf00c9c6

[INFO]  ---> 81d324efe92b

[INFO] Step 4/5 : COPY ${JAR_FILE} app.jar

[INFO]

[INFO]  ---> f11354b41c33

[INFO] Step 5/5 : ENTRYPOINT ["java","-Djava.security.egd=file:/dev/./urandom","-jar","/app.jar"]

[INFO]

[INFO]  ---> Running in 74d40fc4f99c

[INFO] Removing intermediate container 74d40fc4f99c

[INFO]  ---> fbc5e8d75beb

[INFO] Successfully built fbc5e8d75beb

[INFO] Successfully tagged springio/test-springboot:latest

[INFO]

[INFO] Detected build of image with id fbc5e8d75beb

[INFO] Building jar: /home/chench/workspace/java/test-springboot/target/test-springboot-0.0.1-dev-docker-info.jar

[INFO] Successfully built springio/test-springboot:latest

[INFO] ------------------------------------------------------------------------

[INFO] BUILD SUCCESS

[INFO] ------------------------------------------------------------------------

[INFO] Total time: 02:41 min

[INFO] Finished at: 2018-05-07T10:41:05+08:00

[INFO] Final Memory: 47M/132M

[INFO] ------------------------------------------------------------------------

从构建日志中可以很清晰地看到，一开始下载Maven的依赖配置，随后就开始使用Dockerfile中的构建指令定制镜像，并且将项目根路径作为构建上下文。

另外，在项目的target目录下将会生成一个名为docker的目录：

在该docker目录下存在如下几个文件：image-id，image-name，repository，tag，其中保存的就是最新构建出来的镜像信息。

构建完毕之后查看在本地镜像仓库是否存在对应镜像：

$docker image ls

REPOSITORY                 TAG                 IMAGE ID            CREATED             SIZE

springio/test-springboot   latest              fbc5e8d75beb        49 seconds ago      138MB

4.验证镜像是否正确

$docker run --name test-springboot -d -p 8080:8080 springio/test-springboot

438246b5f8e8ed7808b3127ed8fce867cd162f050135369c02f09cb2cdc8d49d

$docker container ps

CONTAINER ID        IMAGE                      COMMAND                  CREATED             STATUS              PORTS                    NAMES

438246b5f8e8        springio/test-springboot   "java -Djava.securit…"   5 seconds ago       Up 4 seconds        0.0.0.0:8080->8080/tcp   test-springboot

而且，还可以直接在docker run命令中传递环境变量设置Spring Boot应用程序的运行环境，如：-e "SPRING_PROFILES_ACTIVE=test"。

$docker run --name test-springboot-env2 -e "SPRING_PROFILES_ACTIVE=test" -p 8080:8080 -d springio/test-springboot

5.将镜像推送到仓库

有2种方式可以实现将构建好的Spring Boot应用程序镜像推送到镜像仓库：

（1）构建完毕之后手动推送

mvn dockerfile:push

（2）配置Maven插件在构建完毕之后自动推送

<!-- 使用Maven插件直接将应用打包为一个Docker镜像 -->

<plugin>

    <groupId>com.spotify</groupId>

    <artifactId>dockerfile-maven-plugin</artifactId>

    <version>1.3.6</version>

    <configuration>

        <repository>${docker.image.prefix}/${project.artifactId}</repository>

        <buildArgs>

            <JAR_FILE>target/${project.build.finalName}.jar</JAR_FILE>

        </buildArgs>

    </configuration>

    <!-- 镜像构建完毕之后自动推送到仓库 -->

    <executions>

        <execution>

            <id>default</id>

            <phase>install</phase>

            <goals>

                <goal>build</goal>

                <goal>push</goal>

            </goals>

        </execution>

    </executions>

</plugin>

注意事项

1.可以使用Maven插件便捷地构建Spring Boot应用程序的Docker镜像，但是最核心的还是如何编写Dockerfile构建脚本。

2.在使用Maven插件构建Spring Boot应用程序镜像时，会使用应用程序根路径作为构建上下文。

【参考】

https://spring.io/guides/gs/spring-boot-docker/

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