I have an annotation which marks classes that contain an inner class which implements a named interface.
Here's an example of how this annotation is used:
public interface Implementable {} @Deserializable(Implementable.class) public class ImplementableFactory { public static Implementable getImplementable() { return new Impl(); } private class Impl implements Implementable {} } And here's the annotation itself:
@Target(ElementType.TYPE) @Retention(RetentionPolicy.RUNTIME) @SupportedSourceVersion(SourceVersion.RELEASE_8) public @interface Deserializable { Class value(); } I'd like to do some annotation processing to ensure this contract. I've created an annotation processor class for that purpose:
public class DeserializableProcessor extends AbstractProcessor { @Override public boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) { for(Element element : roundEnv.getElementsAnnotatedWith(Deserializable.class)){ TypeMirror expected = getDeserializableValue(element); if (expected != null) { Boolean found = false; for (Element enclosed : element.getEnclosedElements()) { if (enclosed.getKind().equals(ElementKind.CLASS)) { //This next bit doesn't compile. //I'm looking for the same functionality. if (expected.isAssignableFrom(enclosed)) { found = true; break; } } } if (!found) { String message = String.format("Classes marked with the Deserializable annotation must contain an inner class with implements the value of the annotation. %s does not contain a class which implements %s.", element.getSimpleName().toString(), expected.toString()); processingEnv.getMessager().printMessage(Diagnostic.Kind.ERROR, message); } } } return true; } private TypeMirror getDeserializableValue(Element element) { ... } } How can I achieve similar functionality to Class::isAssignableFrom within reflection possible via annotation processing?
