Java Reflection Annotation Find findAnnotation(final Class clazz, final Class annotation)

Description

find Annotation

License

Apache License

Declaration

static <T extends Annotation> T findAnnotation(final Class<?> clazz,
            final Class<T> annotation) 

Method Source Code

//package com.java2s;
/*/*  w ww .  j av  a  2  s .  com*/
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import java.lang.annotation.Annotation;

public class Main {
    static <T extends Annotation> T findAnnotation(final Class<?> clazz,
            final Class<T> annotation) {
        checkNotNull(clazz, "clazz is null");
        checkNotNull(annotation, "annotation is null");

        // Check class and parent classes.
        Class<?> currentClazz = clazz;
        while (currentClazz != null) {
            T a = currentClazz.getAnnotation(annotation);
            if (a != null) {
                return a;
            }

            Class<?> enclosingClass = currentClazz.getEnclosingClass();

            while (enclosingClass != null) {
                a = findAnnotation(enclosingClass, annotation);
                if (a != null) {
                    return a;
                }
                enclosingClass = enclosingClass.getEnclosingClass();
            }

            final Class<?>[] interfaces = currentClazz.getInterfaces();
            for (final Class<?> interfaceClass : interfaces) {
                a = findAnnotation(interfaceClass, annotation);
                if (a != null) {
                    return a;
                }
            }

            currentClazz = currentClazz.getSuperclass();
        }

        return null;
    }

    static <T> T checkNotNull(final T value, final String msg) {
        if (value == null) {
            throw new NullPointerException(msg);
        }

        return value;
    }
}

Related

1. findAnnotation(Class clazz, Class annotationClass)
2. findAnnotation(Class clazz, Class annotationClass)
3. findAnnotation(Class clazz, Class annotationType)
4. findAnnotation(Class klass, Class annotationClass)
5. findAnnotation(final Class clazz, final Class type)
6. findAnnotation(final Class type, final Class annotationType)
7. findAnnotation(final Class targetAnnotation, final Class annotatedType)
8. findAnnotation(final Class annotationClass, final Class beanClass, final Field field)
9. findAnnotation(final Set annotations, final Class annotationType)