Java Reflection Annotation getAnnotation(Class clazz, Class annotationClass)

Description

get Annotation

License

Apache License

Declaration

public static <R extends Annotation> R getAnnotation(Class<?> clazz, Class<R> annotationClass) 

Method Source Code

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

import java.lang.annotation.Annotation;

import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;

public class Main {
    public static <R extends Annotation> R getAnnotation(Class<?> clazz, Class<R> annotationClass) {
        return (R) findAnnotation(clazz, annotationClass, new HashSet<>());
    }/*  www  . j  av a 2  s  . co  m*/

    private static Annotation findAnnotation(Class<?> clazz, Class<? extends Annotation> annotationClass,
            Set<Class<?>> set) {
        if (clazz == null || set.contains(clazz) || clazz.equals(Object.class)) {
            return null;
        }

        set.add(clazz);

        Annotation result = findAnnotation(clazz.getSuperclass(), annotationClass, set);

        if (result != null) {
            return result;
        }

        Annotation findResult = Arrays.stream(clazz.getInterfaces())
                .map((Class<?> interf) -> findAnnotation(interf, annotationClass, set))
                .filter((Annotation annotation) -> annotation != null).findFirst().orElse(null);

        if (findResult != null) {
            return findResult;
        }

        Annotation interfaceAnnotation = Arrays.stream(clazz.getDeclaredAnnotations())
                .filter((Annotation annotation) -> annotation.annotationType().equals(annotationClass)).findFirst()
                .orElse(null);

        if (interfaceAnnotation != null) {
            return interfaceAnnotation;
        }

        return Arrays.stream(clazz.getDeclaredAnnotations())
                .map((Annotation annotation) -> findAnnotation(annotation.annotationType(), annotationClass, set))
                .filter((Annotation annotation) -> annotation != null).findFirst().orElse(null);
    }
}

Related

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2. getAnnotation(Class classForAnnotation, Class annotationClass)
3. getAnnotation(Class clazz, Class annotationClass)
4. getAnnotation(Class clazz, Class annotationClass)
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6. getAnnotation(Class clazz, Class ann)
7. getAnnotation(Class clazz, Class annClazz)
8. getAnnotation(Class clazz, Class annotation)
9. getAnnotation(Class clazz, Class annotation)