如何使用 Windows 命令行构建最简单的多模块 Maven 项目？

Question

我有一个非常简单的多模块项目。

目录结构：

   C:\acme-project\parent
   C:\acme-project\alpha   
   C:\acme-project\beta

逻辑结构：

     parent
    /     \
 alpha <- beta

我无法构建beta，因为它依赖于alpha。而且 Meven 不想在 Beta 版的构建过程中构建 alpha！

C:\acme-project\beta> mvn package
[INFO] Scanning for projects...
[INFO]                                                                         
[INFO] ------------------------------------------------------------------------
[INFO] Building beta 1.0-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[WARNING] The POM for com.company:alpha:jar:1.0-SNAPSHOT is missing, no dependency information available
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 1.263 s
[INFO] Finished at: 2017-03-28T15:00:34+03:00
[INFO] Final Memory: 16M/220M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal on project beta: Could not resolve dependencies for project com.company:beta:jar:1.0-SNAPSHOT: The following artifacts could not be resolved: com.company:alpha:jar:1.0-SNAPSHOT: Could not find artifact com.company:alpha:jar:1.0-SNAPSHOT -> [Help 1]
[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/DependencyResolutionException

我的 POM：

C:\acme-project\parent\parent.pom：

<?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>

  <groupId>com.company</groupId>
  <artifactId>parent</artifactId>
  <version>1</version>
  <packaging>pom</packaging>

  <modules>
    <module>../alpha</module>
    <module>../beta</module>    
  </modules>
</project>

C:\acme-project\alpha\alpha.com：

<?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/xsd/maven-4.0.0.xsd">
  <parent>
    <artifactId>parent</artifactId>
    <groupId>com.company</groupId>
    <version>1</version>
    <relativePath>../parent/pom.xml</relativePath>
  </parent>
  <modelVersion>4.0.0</modelVersion>

  <artifactId>alpha</artifactId>
  <version>1.0-SNAPSHOT</version>

</project>

C:\acme-project\beta\beta.pom：

<?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/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <parent>
    <groupId>com.company</groupId>
    <artifactId>parent</artifactId>
    <version>1</version>
    <relativePath>../parent/pom.xml</relativePath>
  </parent>

  <artifactId>beta</artifactId>
  <version>1.0-SNAPSHOT</version>
  <packaging>jar</packaging>

  <dependencies>
    <dependency>
      <groupId>com.company</groupId>
      <artifactId>alpha</artifactId>
      <version>1.0-SNAPSHOT</version>
    </dependency>
  </dependencies>
</project>

我可以在 C:...\parent 中构建运行 mvn package 的 acme 项目。但如果项目更复杂，parent 可能有 100 个子模块。显然我不想为了让 Maven 开心而构建 98 个模块（beta 不依赖的其他模块）。

Answer 1

如果您只想构建 beta 所依赖的项目，请转到根聚合器（即，所有 <modules> 的项目；在您的情况下为 parent），然后让 Maven 仅构建 @ 987654324@ 和它在当前反应堆中的依赖：

cd parent
mvn package --projects com.company:beta --also-make

仅供参考，这可以缩写：

mvn package -pl :beta -am

在您的最小示例中，上述命令仍将构建所有内容（因为 beta 依赖于 alpha 并隐含在 parent 上），但在较大的反应器中，它只会构建构建 @987654330 所需的最小子集@。