Java Inherited Annotation

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Syntax and Declaration

import java.lang.annotation.*;

@Inherited
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.TYPE)
public @interface InheritedAnnotation {
    String value() default "default";
}

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Technical Mechanics and Limitations

1. Class-Level Restriction: @Inherited only affects annotations applied to class declarations (ElementType.TYPE). It has absolutely no effect if the annotation is applied to methods, fields, constructors, or local variables. Subclass methods do not inherit annotations from overridden superclass methods, regardless of the @Inherited meta-annotation.
2. Class Extension vs. Interface Implementation: The inheritance mechanism strictly follows class extension (extends). It does not apply to interface implementation (implements).
   • If an interface is annotated with an @Inherited annotation, classes that implement that interface will not inherit the annotation.
   • If a sub-interface extends a super-interface annotated with an @Inherited annotation, the sub-interface will not inherit the annotation.
3. Reflection Resolution: The inheritance is resolved at runtime via the java.lang.Class reflection API. When Class.getAnnotation(Class<A> annotationClass) is invoked:
   • The JVM first checks if the annotation is directly present on the target class.
   • If absent, and the annotation type is meta-annotated with @Inherited, the JVM queries the superclass.
   • This recursive traversal continues up the inheritance tree until the annotation is found or java.lang.Object is reached.

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Behavior Visualization

// 1. Superclass application
@InheritedAnnotation("SuperClassData")
public class SuperClass { }

// SubClass inherits the annotation from SuperClass
public class SubClass extends SuperClass { }

// 2. Interface application
@InheritedAnnotation("InterfaceData")
public interface BaseInterface { }

// ImplementingClass DOES NOT inherit the annotation
public class ImplementingClass implements BaseInterface { }

// Returns true
boolean hasSubClassAnnotation = SubClass.class.isAnnotationPresent(InheritedAnnotation.class);

// Returns "SuperClassData"
InheritedAnnotation subClassAnn = SubClass.class.getAnnotation(InheritedAnnotation.class);

// Returns false (Interfaces do not pass down inherited annotations)
boolean hasImplAnnotation = ImplementingClass.class.isAnnotationPresent(InheritedAnnotation.class);

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Annotation Overriding

@InheritedAnnotation("Parent")
public class ParentClass { }

@InheritedAnnotation("Child")
public class ChildClass extends ParentClass { }

// Reflection on ChildClass.class.getAnnotation(InheritedAnnotation.class) 
// will yield an annotation with the value "Child".