Java Reflection Annotation Find findAnnotation(final Class type, final Class annotationType)

License

Parameter

Return

Declaration

@Nullable
public static <A extends Annotation> A findAnnotation(final Class<?> type, final Class<A> annotationType) 

Method Source Code

//package com.java2s;
//License from project: Apache License 

import java.lang.annotation.Annotation;
import java.lang.reflect.*;

import javax.annotation.Nullable;

public class Main {
    /**//w  w w . j  a va  2  s  . c o  m
     * Recursively search a type's inheritance hierarchy for an annotation.
     *
     * @param type           The class whose hierarchy to search.
     * @param annotationType The annotation type to search for.
     * @param <A>            The annotation type.
     *
     * @return The annotation of the given annotation type in the given type's hierarchy or {@code null} if the type's hierarchy
     * contains no classes that have the given annotation type set.
     */
    @Nullable
    public static <A extends Annotation> A findAnnotation(final Class<?> type, final Class<A> annotationType) {

        A annotation = type.getAnnotation(annotationType);
        if (annotation != null) {
            return annotation;
        }

        for (final Class<?> subType : type.getInterfaces()) {
            annotation = findAnnotation(subType, annotationType);
            if (annotation != null) {
                return annotation;
            }
        }
        if (type.getSuperclass() != null) {
            annotation = findAnnotation(type.getSuperclass(), annotationType);
            if (annotation != null) {
                return annotation;
            }
        }

        return null;
    }

    /**
     * Recursively search a method's inheritance hierarchy for an annotation.
     *
     * @param method         The method whose hierarchy to search.
     * @param annotationType The annotation type to search for.
     * @param <A>            The annotation type.
     *
     * @return The annotation of the given annotation type in the given method's hierarchy or {@code null} if the method's hierarchy
     * contains no methods that have the given annotation type set.
     */
    @Nullable
    public static <A extends Annotation> A findAnnotation(final Method method, final Class<A> annotationType) {

        A annotation = method.getAnnotation(annotationType);
        if (annotation != null) {
            //logger.debug( "Found annotation {} on {}", annotationType, method );
            return annotation;
        }

        //logger.debug( "Digging down method for annotation {}, {}", annotationType, method );

        Method superclassMethod = null;
        Class<?> superclass = method.getDeclaringClass();
        while ((superclass = superclass.getSuperclass()) != null) {
            try {
                //logger.debug( "Trying for method {} in {}", method.getName(), superclass );
                superclassMethod = superclass.getMethod(method.getName(), method.getParameterTypes());
            } catch (final NoSuchMethodException ignored) {
            }
        }
        if (superclassMethod == null) {
            //logger.debug( "Gave up for annotation {} (reached end of hierarchy)", annotationType );
            return null;
        }

        return findAnnotation(superclassMethod, annotationType);
    }
}

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