Question

There is a multi-module Maven-3 project, where one of sub-modules is used as <dependency> in all other modules. At the same time, all sub-modules inherit from parent module. Such a structure leads to cyclic dependency. How can I resolve it?

Project structure is rather typical:

/foo
  /foo-testkit
  /foo-core

This is parent foo/pom.xml:

[...]
<build>
  <plugins>
    <plugin>
      <groupId>org.apache.maven.plugins</groupId>
      <artifactId>maven-checkstyle-plugin</artifactId>
      <configuration>
        <configLocation>checkstyle/checks.xml</configLocation>
      </configuration>
      <dependencies>
        <dependency>
          <groupId>${project.groupId}</groupId>
          <artifactId>foo-testkit</artifactId>
          <version>${project.version}</version>
        </dependency>
      </dependencies>
      <executions>
        <execution>
          <phase>prepare-package</phase>
          <goals>
            <goal>check</goal>
          </goals>
        </execution>
      </executions>
    </plugin>
  </plugins>
</build>
[...]

In parent foo/pom.xml I specify how and when checkstyle plugin has to be executed in every sub-module. But I don’t need checkstyle to be executed in foo-testkit, which is a sub-module inheriting from foo, but is at the same time a dependency..

Answer 1

One way is to disable the checkstyle plugin for module foo-testkit by adding the below to foo-testkit’s pom.xml file.

<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-checkstyle-plugin</artifactId>
  <configuration>
    <skip>true</skip>
  </configuration>
</plugin>

If that is not to your liking, another way is to move the checkstyle plugin configuration from build/plugins to build/pluginManagment/plugins in the parent pom.xml file. Then in each module you want checkstyle executed, add this to the build/plugins section of each module’s pom.xml file:

<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-checkstyle-plugin</artifactId>
</plugin>

This invokes the plugin for that module and the configuration specified in the parent pom.xml under the pluginManagement section will be applied. You can verify that is working correctly by running mvn help:effective-pom on that module.