Question

我在使用Maven的SNAPSHOT构建中进行构建排序时遇到问题。反应堆正以无效的顺序建造所有罐子。

以下是重新创建问题的示例结构（我遇到问题的项目要大得多，> 100罐）：

pom.xml        [reactor]
parent/pom.xml [parent]
jar1/pom.xml
jar2/pom.xml
jar3/pom.xml

pom.xml [reactor]

<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>
  <packaging>pom</packaging>
  <groupId>com.test.buildorder</groupId>
  <artifactId>reactor</artifactId>
  <version>1.0</version>
  <modules>
    <module>jar3</module>
    <module>jar2</module>
    <module>jar1</module>
  </modules>
</project>

父/ pom.xml的

<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>
  <groupId>com.test.buildorder</groupId>
  <artifactId>parent</artifactId>
  <version>1.1</version>
  <packaging>pom</packaging>

  <dependencyManagement>
  <dependencies>
      <dependency>
        <groupId>com.test.buildorder</groupId>
        <artifactId>jar1</artifactId>
        <version>1.1</version>
      </dependency>
      <dependency>
        <groupId>com.test.buildorder</groupId>
        <artifactId>jar2</artifactId>
        <version>1.0</version>
      </dependency>
      <dependency>
        <groupId>com.test.buildorder</groupId>
        <artifactId>jar3</artifactId>
        <version>1.1</version>
      </dependency>
    </dependencies>
  </dependencyManagement>
</project>

jar1 / pom.xml的

<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>
  <groupId>com.test.buildorder</groupId>
  <artifactId>jar1</artifactId>
  <version>1.1</version>
  <parent>
    <groupId>com.test.buildorder</groupId>
    <artifactId>parent</artifactId>
    <version>1.1</version>
  </parent>
</project>

jar2 / pom.xml的

<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>
  <groupId>com.test.buildorder</groupId>
  <artifactId>jar2</artifactId>
  <version>1.1</version>
  <parent>
    <groupId>com.test.buildorder</groupId>
    <artifactId>parent</artifactId>
    <version>1.0</version>
  </parent>

  <dependencies>
    <dependency>
      <groupId>com.test.buildorder</groupId>
      <artifactId>jar1</artifactId>
    </dependency>
  </dependencies>
</project>

jar3 / pom.xml的

<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>
  <groupId>com.test.buildorder</groupId>
  <artifactId>jar3</artifactId>
  <version>1.1</version>
  <parent>
    <groupId>com.test.buildorder</groupId>
    <artifactId>parent</artifactId>
    <version>1.1</version>
  </parent>

  <dependencies>
    <dependency>
      <groupId>com.test.buildorder</groupId>
      <artifactId>jar2</artifactId>
    </dependency>
  </dependencies>
</project>

我的存储库（在本例中为本地）只有每个jar的已发布1.0版本，jar3-1.0依赖于jar2-1.0，而jar2-1.0依赖于jar1-1.0并且每个都有父级1.0（我可以发布这个代码，如果需要，但我的问题已经很长，所以我会推迟，除非问）。

我现在安装上面的1.1父pom，然后尝试在reactor上运行安装并获得以下结果。

[INFO] Scanning for projects...
[WARNING]
[WARNING] Some problems were encountered while building the effective model for com.test.buildorder:jar3:jar:1.1
[WARNING] 'parent.relativePath' points at com.test.buildorder:reactor instead of com.test.buildorder:parent, please verify your project structure @ line 6, column 11
[WARNING]
[WARNING] Some problems were encountered while building the effective model for com.test.buildorder:jar2:jar:1.1
[WARNING] 'parent.relativePath' points at com.test.buildorder:reactor instead of com.test.buildorder:parent, please verify your project structure @ line 6, column 11
[WARNING]
[WARNING] Some problems were encountered while building the effective model for com.test.buildorder:jar1:jar:1.1
[WARNING] 'parent.relativePath' points at com.test.buildorder:reactor instead of com.test.buildorder:parent, please verify your project structure @ line 6, column 11
[WARNING]
[WARNING] It is highly recommended to fix these problems because they threaten the stability of your build.
[WARNING]
[WARNING] For this reason, future Maven versions might no longer support building such malformed projects.
[WARNING]
[INFO] ------------------------------------------------------------------------
[INFO] Reactor Build Order:
[INFO]
[INFO] jar3
[INFO] jar2
[INFO] jar1
[INFO] reactor
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] Building jar3 1.1
[INFO] ------------------------------------------------------------------------
Downloading: https://repo.maven.apache.org/maven2/com/test/buildorder/jar1/1.1/jar1-1.1.jar
[INFO] ------------------------------------------------------------------------
[INFO] Reactor Summary:
[INFO]
[INFO] jar3 ............................................... FAILURE [  0.645 s]
[INFO] jar2 ............................................... SKIPPED
[INFO] jar1 ............................................... SKIPPED
[INFO] reactor ............................................ SKIPPED
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 0.775 s
[INFO] Finished at: 2015-06-03T16:56:04-05:00
[INFO] Final Memory: 4M/15M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal on project jar3: Could not resolve dependencies for project com.test.buildorder:jar3:jar:1.1: Could not find artifact com.test.buildorder:jar1:jar:1.1 in central (https://repo.maven.apache.org/maven2) -> [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

当我构建1.0版本时，Reactor足够聪明，可以实现依赖树jar3-1.0 - ＆gt; jar2-1.0 - ＆gt; jar1-1.0并以jar1，jar2，jar3的顺序构建以满足依赖性。

现在因为jar3-1.1依赖于jar2-1.0（在repo中），反应器不会假设首先需要构建jar1，但是debug（使用-X参数）显示依赖树为：

[DEBUG] com.test.buildorder:jar3:jar:1.1
[DEBUG]    com.test.buildorder:jar2:jar:1.0:compile
[DEBUG]       com.test.buildorder:jar1:jar:1.1:compile (version managed from 1.0 by com.test.buildorder:parent:1.1)

所以我对这个场景有几个问题：
1.为什么maven认为jar3-1.1对jar1-1.1有传递依赖性？
2.为什么反应堆没有意识到这种传递依赖性并建立满足它的所需顺序？ 3.如何防止此问题发生？（最好不要重写超过100个poms。）

编辑：找到问题一的答案，以及问题三的一个解决方案。但是仍然希望听到问题二。

1 。因为我从未为依赖关系定义范围，所以maven确定已分配默认范围compile。因此，从jar2到jar1的依赖关系将显示为依赖于jar2的jar的传递依赖（例如jar3）。 (version managed from 1.0 by com.test.buildorder:parent:1.1)告诉我依赖是从jar2-1.0到jar1-1.0但是因为父指定了jar 1（1.1）的另一个版本，所以它需要。

3 。如果我将依赖项的范围从jar2更改为jar1到provided，则依赖项不再变为可传递。 这假设在运行时所需的罐子都存在，所以这可能不是每个遇到此问题的人的解决方案。 Here is a guide to the scopes available in Maven

Answer 1

我安装了所有项目，所有版本都设置为1.0。然后我按照你的说法更改了版本并得到了同样的错误。

将reactor POM更改为：

 <modules>
    <module>jar1</module>
    <module>jar2</module>
    <module>jar3</module>
</modules>

......构建成功。

我查看了Guide to Working with Multiple Modules, Reactor Sorting，最后一个选项是：

<modules>元素中声明的顺序（如果没有其他规则适用）

在阅读下一句“注意，仅使用”实例化“引用 - dependencyManagement和pluginManagement元素不会导致更改反应堆排序顺序”：

我恢复了reactor POM
我对<dependencyManagement> POM中的parent部分进行了评论，并明确地将<version>添加到jar2和jar3 POM中→构建成功了：

[INFO] Reactor Build Order
[INFO]
[INFO] jar3
[INFO] jar1
[INFO] jar2
[INFO] reactor

Answer 2

[警告]构建有效时遇到了一些问题 com.test.buildorder的模型：jar3：jar：1.1 [警告] ＆＃39; parent.relativePath＆＃39;指向com.test.buildorder：reactor而不是 com.test.buildorder：父母，

由于您的反应堆不是父级，我认为您需要明确定义相对路径

<parent>
    <groupId>com.test.buildorder</groupId>
    <artifactId>parent</artifactId>
    <version>1.1</version>
    <relativePath>../parent</relativePath>
  </parent>

此外，您有jar2 1.0和1.1的不同版本。对齐他们

Answer 3

问题2：Maven反应堆排序不适用于传递依赖关系，它仅计算直接依赖关系：

jar3-1.1取决于jar2-1.0（不在反应堆中）
jar2-1.1取决于jar1-1.1
jar1-1.1

在这种情况下，从jar3-1.1到jar1-1.1没有链接

我们不希望您将反应堆中的jar2-1.1与您的dependencyManagement中的jar2-1.0混合

Maven reactor构建顺序不满足所有依赖项

3 个答案: