在脱机构建中缓存Maven父级

Question

TL/DR:我如何缓存pom.xml文件,<parent>以便我的构建可以在离线模式下运行？

我正在使用Docker来构建一个maven项目.我的目标是为构建添加两个步骤:一个用于下载所有依赖项,另一个用于构建项目.这是我的Dockerfile到目前为止的样子:

FROM maven:3.3-jdk-8

# Download the project dependencies (so they can be cached by Docker)
ADD pom.xml /runtime/
WORKDIR /runtime
RUN mvn dependency:go-offline
RUN mvn dependency:resolve-plugins

# Mount the local repository
ADD . /runtime

# Build the service
RUN mvn clean package -o -DskipTests

这似乎适用于插件.我查了一下/root/.m2/repository,一切似乎都井然有序.

编辑:当仔细检查/root/.m2/repository目录时,它不再存在.出于某种原因,Maven没有将任何依赖项保存到此位置.

编辑2:构建Docker镜像后,没有/root/.m2/repository目录.但是,如果我mvn dependency:go-offline在Docker容器内的shell中运行,则创建目录时没有问题.

当我尝试构建我的应用程序时,我收到以下错误:

[ERROR] [ERROR] Some problems were encountered while processing the POMs:
[FATAL] Non-resolvable parent POM for com.example:service:1.2: Cannot access central (http://jcenter.bintray.com) in offline mode and the artifact org.springframework.boot:spring-boot-starter-parent:pom:1.4.0.M3 has not been downloaded from it before. and 'parent.relativePath' points at wrong local POM @ line 14, column 13
 @
[ERROR] The build could not read 1 project -> [Help 1]
[ERROR]
[ERROR]   The project com.sample:service:1.2 (/runtime/pom.xml) has 1 error
[ERROR]     Non-resolvable parent POM for com.oe:graph-service:1.2: Cannot access central (http://jcenter.bintray.com) in offline mode and the artifact org.springframework.boot:spring-boot-starter-parent:pom:1.4.0.M3 has not been downloaded from it before. and 'parent.relativePath' points at wrong local POM @ line 14, column 13 -> [Help 2]
[ERROR]
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR]
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/ProjectBuildingException
[ERROR] [Help 2] http://cwiki.apache.org/confluence/display/MAVEN/UnresolvableModelException

问题似乎mvn dependency:go-offline是没有解决父母问题.当我在离线模式下运行构建时,它会中断.

以下是我的pom.xml文件的相关部分:

<?xml version="1.0" encoding="UTF-8"?>

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
    <modelVersion>4.0.0</modelVersion>

    ...

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.4.0.M3</version>
    </parent>

    ...

    <repositories>
        <repository>
            <snapshots>
                <enabled>false</enabled>
            </snapshots>
            <id>central</id>
            <name>bintray</name>
            <url>http://jcenter.bintray.com</url>
        </repository>

        <repository>
            <id>repository.springsource.snapshot</id>
            <name>SpringSource Snapshot Repository</name>
            <url>http://repo.springsource.org/snapshot</url>
        </repository>

        <repository>
            <id>spring-milestones</id>
            <url>http://repo.spring.io/milestone</url>
        </repository>
    </repositories>

    <dependencies>
       ...

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
            <exclusions>
                <exclusion>
                    <groupId>org.springframework.boot</groupId>
                    <artifactId>spring-boot-starter-tomcat</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-jetty</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.scala</groupId>
            <artifactId>spring-scala_2.11</artifactId>
            <version>1.0.0.BUILD-SNAPSHOT</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-security</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-jdbc</artifactId>
        </dependency>
        <!-- disabling Spring cloud AWS until proper testing harnesses can be set up -->
        <dependency>
            <groupId>org.apache.httpcomponents</groupId>
            <artifactId>httpcore</artifactId>
            <version>LATEST</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-aws-autoconfigure</artifactId>
            <version>1.1.0.RELEASE</version>
        </dependency>

        ...
    </dependencies>

    ...
</project>

Answer 1

如果您自定义 maven 的settings.xml文件，您可以将存储库文件保存在映像上。

创建 的自定义版本settings.xml，并localRepository修改设置，如下所示：

<settings xmlns="http://maven.apache.org/SETTINGS/1.0.0"
          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
          xsi:schemaLocation="http://maven.apache.org/SETTINGS/1.0.0 http://maven.apache.org/xsd/settings-1.0.0.xsd">
  <!-- localRepository
   | The path to the local repository maven will use to store artifacts.
   |
   | Default: ${user.home}/.m2/repository -->
  <localRepository>/usr/share/maven/repo</localRepository>
...

然后在构建镜像时覆盖默认配置：

FROM maven:3-jdk-8

COPY settings.xml /usr/share/maven/conf/settings.xml

RUN mkdir -p /usr/src/app
WORKDIR /usr/src/app

ADD . /usr/src/app

RUN mvn dependency:go-offline

RUN mvn clean package

现在您的存储库存储在/usr/share/maven/repo.

使用onbuild

您还可以使用ONBUILD创建基础映像，这将允许为每个 Maven 项目自定义配置映像。

像这样：

FROM maven:3-jdk-8

COPY settings.xml /usr/share/maven/conf/settings.xml

RUN mkdir -p /usr/src/app
WORKDIR /usr/src/app

ONBUILD ADD . /usr/src/app

ONBUILD RUN mvn dependency:go-offline

ONBUILD RUN mvn clean package

然后构建图像：

docker build -t mvn_bldr .

这将为其他 Maven 映像创建模板。然后您可以使用以下命令创建自定义下游图像：

FROM mvn_bldr

如果您想进一步自定义图像，您可以添加更多指令，模板的每条指令都会在命令之后触发FROM mvn_bldr，如文档中所示：

触发器将在下游构建的上下文中执行，就像它是在下游 Dockerfile 中的 FROM 指令之后立即插入的一样。