Parent

Links#

https://maven.apache.org/guides/introduction/introduction-to-the-pom.html
https://maven.apache.org/ref/current/maven-model/maven.html

1. Important Points#

parent POM:
    被当前项目继承的 POM，用来统一 properties、dependencyManagement、pluginManagement

effective POM:
    super POM + parent POM + current POM + active profiles 合并后的结果

./mvnw help:effective-pom
./mvnw help:active-profiles

2. Parent Declaration#

<parent>
  <groupId>com.example.platform</groupId>
  <artifactId>platform-parent</artifactId>
  <version>1.2.0</version>
  <relativePath>../pom.xml</relativePath>
</parent>

relativePath:
    先从本地路径找 parent
    不需要本地 parent 时可写空值

<relativePath/>

3. What Is Inherited#

Area	Inherited	Notes
`properties`	yes	child can override
`dependencyManagement`	yes	controls default dependency versions
`dependencies`	yes	use carefully; can force every child to include dependencies
`pluginManagement`	yes	recommended place for plugin versions
`plugins`	yes	executions may run in child modules
`repositories`	yes	better keep repository policy centralized
`profiles`	limited	activation and inherited effects need effective POM check

4. Recommended Parent POM#

<project>
  <modelVersion>4.0.0</modelVersion>
  <groupId>com.example.platform</groupId>
  <artifactId>platform-parent</artifactId>
  <version>1.2.0</version>
  <packaging>pom</packaging>

  <properties>
    <java.version>21</java.version>
    <maven.compiler.release>${java.version}</maven.compiler.release>
  </properties>

  <dependencyManagement>
    <dependencies>
      <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-dependencies</artifactId>
        <version>3.3.1</version>
        <type>pom</type>
        <scope>import</scope>
      </dependency>
    </dependencies>
  </dependencyManagement>

  <build>
    <pluginManagement>
      <plugins>
        <plugin>
          <groupId>org.apache.maven.plugins</groupId>
          <artifactId>maven-compiler-plugin</artifactId>
          <version>3.13.0</version>
        </plugin>
      </plugins>
    </pluginManagement>
  </build>
</project>

5. Child Override#

<properties>
  <java.version>17</java.version>
</properties>

<dependencyManagement>
  <dependencies>
    <dependency>
      <groupId>com.fasterxml.jackson.core</groupId>
      <artifactId>jackson-databind</artifactId>
      <version>2.17.2</version>
    </dependency>
  </dependencies>
</dependencyManagement>

override rule:
    child POM can override many parent defaults
    verify final result with effective-pom

6. Plugin Inheritance#

<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-checkstyle-plugin</artifactId>
  <version>3.4.0</version>
  <inherited>false</inherited>
</plugin>

inherited=false:
    parent config does not propagate to child modules
    useful for aggregator-only plugins

7. Common Mistakes#

parent not found:
    check relativePath, repository, and version

plugin version unclear:
    inspect effective POM
    move version to pluginManagement

child override seems ignored:
    check property name
    check active profiles
    check dependencyManagement order