Generating source code with a gradle task based on existing classes with annotations on them

I am creating springboot applications, and most of the time I find myself writing boilerplate code for my models - repositories, services, controllers, builders... I do not want to do that.

Based on my my experiences, previous works and researches I have a concept kind of developed in my mind. Basically the following:

1. I create an annotation

@Target(ElementType.TYPE)
@Retention(RetentionPolicy.SOURCE)
public @interface CodeGenSubject {
}

2. I create a processor

public class MyProcessor extends AbstractProcessor {
    @Override
    public Set<String> getSupportedAnnotationTypes() {
        return Collections.singleton(CodeGenSubject.class.getCanonicalName());
    }

    @Override
    public boolean process(Set<? extends TypeElement> set, RoundEnvironment roundEnvironment) {
        for(Element e: roundEnvironment.getElementsAnnotatedWith(CodeGenSubject.class)){
            // Observe fields and methods with reflection API
            // "Write" some code with JavaPoet
            // Place the generated code to the src/java folder
            // (with javax.annotation.processing.Filer)
        }
    }
}

3. I write my domain specific class

@CodeGenSubject
@Entity
public class MyDomainSpecificEntity {
    @Id
    private Long id;
    private String stuff;

    // getters and setters
}

4. And lasty, I create a gradle task (?)

task myCodeGeneratorTask(type: ???, group: "", desription: "") {
    // With this I am stuck
}

Ideally this template generator would be a separate module.

I have seen some example projects (mostly for android), and then I found the most promising:

https://www.baeldung.com/java-annotation-processing-builder

Would be perfect, but... it uses maven, and the code is placed in a totally impenetrable repository with a pom.xml file in the root project with a few thousand lines. Thanks : D

Right now I am working on an example multi-module gradle project with a springboot application. I have one entity (MyDomainSpecificEntity) and I am trying to make gradle generate some source code for me based on my annotation and processor.

Firstly, the biggest help would be some advice if I am conceptually wrong.

Secondly, if I am not, I would appreciate some help with that gradle script.

Lastly... the best would be a cleansed example project, If anyone ever played with this subject, and have some sort of public repo, that would be the most welcome.

Thanks.