How to run a plugin only for "war" package type in Maven?

Question

Provided two Maven projects: J (jar), W (war); both depend on one parent P (pom). The parent has a plugin, which must only run for the project "W".

How does one go about doing this:

• without creating separate parent projects
• without using a profile (so build must still be executed with mvn clean package)

J (jar)

<project>
  <parent>
    <artifactId>P</artifactId>
  </parent>
  <artifactId>J</artifactId>
  <packaging>jar</packaging>
</project>

W (war)

<project>
  <parent>
    <artifactId>P</artifactId>
  </parent>
  <artifactId>W</artifactId>
  <packaging>war</packaging>
</project>

P (pom)

<project>
  <artifactId>P</artifactId>
  <packaging>pom</packaging>

  <build>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-jar-plugin</artifactId>
        <executions>
          <execution>
            <phase>package</phase>
            <goals>
              <goal>jar</goal>
            </goals>
            <configuration>
              <classifier>classes</classifier>
            </configuration>
          </execution>
        </executions>
      </plugin>
    </plugins>
  </build>
</project>

Answer 1

I think you can achieve this using Profile Activation. Ideally, the activation condition would be something like "packaging type is war", but apparently, this condition cannot be implemented in Maven. However, in your case, there is a condition that can be implemented and that is probably equivalent in practice: "there is a src/main/webapp directory".

This is how your pom.xml might look like:

<profiles>
    <profile>
        <activation>
            <file>
                <exists>src/main/webapp</exists>
            </file>
        </activation>
        <build>
            [plugin configuration]
        </build>
    </profile>
</profiles>