TL/DR:如何缓存 pom.xml文件的 <parent>所以我的构建可以在离线模式下运行？
我正在使用 Docker 构建一个 Maven 项目。我的目标是在构建中添加两个步骤:一个是下载所有依赖项，另一个是构建项目。到目前为止，这是我的 Dockerfile 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。我检查了 /root/.m2/repository一切似乎都井井有条。
编辑:仔细检查 /root/.m2/repository 时目录，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，如果我运行 mvn dependency:go-offline从 Docker 容器内的 shell 中，可以毫无问题地创建目录。
当我尝试构建我的应用程序时，出现以下错误:
[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
问题似乎是mvn dependency:go-offline没有解决 parent 。当我在离线模式下运行构建时，它中断了。
这是我的 pom.xml 的相关部分文件:
<?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>
最佳答案
如果您自定义 Maven 的 settings.xml 文件，您可以将存储库文件保存在图像上。
创建自定义版本的 settings.xml，修改 localRepository 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 中。
使用构建
您还可以使用 ONBUILD 创建基本图像，这将允许为每个 Maven 项目自定义配置图像。
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
然后构建镜像:
docker build -t mvn_bldr .
这将为其他 Maven 图像创建一个模板。然后您可以创建自定义下游图像:
FROM mvn_bldr
如果您想进一步自定义您的图像，您可以添加更多指令，模板的每条指令都将在 FROM mvn_bldr 命令之后触发，如文档中所示:
The trigger will be executed in the context of the downstream build, as if it had been inserted immediately after the FROM instruction in the downstream Dockerfile.
关于java - 在离线构建中缓存 Maven parent，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/40898608/