[FIXED] Remove parent from Maven Shade dependency reduced pom with Flatten

Issue

The project has the following structure:

FatJarRootPom has dependencies for X and Y. FatJarA and FatJarB all declare FatJarRootPom as their parent so they get its dependencies X and Y shaded into their JAR along with their own dependencies.

The issue is that, Shade Plugin will leave reference to parent in the dependency-reduced-pom.xml so FatJarA's pom will still explicitly depend on X and Y despite having them inside JAR already.

Flatten Plugin can get rid of parent so it would be optimal to run Shade Plugin on flattened pom. It will process all dependencies and then remove them from dependency-reduced-pom.xml. However, when I configure Flatten Plugin, Shade Plugin will not pick up its output and will still produce incorrect pom.

I have found this answer which suggests changing the invocation order of shade and flatten so that shade comes first, but it won't work since dependencies from FatJarRootPom will still be in the pom, which I am trying to avoid.

Maybe there is some other way of just removing parent section from dependency-reduced-pom.xml without flatten plugin?

Update: I have tried changing my FatJarRootPom to a POM dependency FatJarPom with transitive dependencies listed in it, and amusingly, Maven Shade Plugin will specifically skip POM dependency and will not remove it from dependency reduced POM, even as it would mean that all shaded dependencies will absolutely appear as dependencies of fat-jar artifact.

Solution

I have overlooked that Flatten Plugin has "fatjar" mode which will strip all dependencies. It is a very coarse grained approach, but it should do in my use case.

So the solution is placing

            <plugin>
                <groupId>org.codehaus.mojo</groupId>
                <artifactId>flatten-maven-plugin</artifactId>
                <version>1.2.7</version>
                <executions>
                    <execution>
                        <id>flatten</id>
                        <phase>package</phase>
                        <goals>
                            <goal>flatten</goal>
                        </goals>
                        <configuration>
                            <updatePomFile>true</updatePomFile>
                            <flattenMode>fatjar</flattenMode>
                        </configuration>
                    </execution>
                    ...

after the corresponding Shade Plugin section.

Answered By - alamar
Answer Checked By - Pedro (JavaFixing Volunteer)