Java Reflection Annotation getAnnotation(Class onClass, Class desiredAnnotationClass)

License

Parameter

Return

Declaration

public static <A extends Annotation> A getAnnotation(Class<?> onClass,
        Class<A> desiredAnnotationClass) 

Method Source Code

//package com.java2s;
/*/*from w w w.jav a2  s . c  om*/
 * File: ReflectionHelper.java
 *
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 *
 * The contents of this file are subject to the terms and conditions of 
 * the Common Development and Distribution License 1.0 (the "License").
 *
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the License by consulting the LICENSE.txt file
 * distributed with this file, or by consulting https://oss.oracle.com/licenses/CDDL
 *
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing the software, include this License Header Notice in each
 * file and include the License file LICENSE.txt.
 *
 * MODIFICATIONS:
 * If applicable, add the following below the License Header, with the fields
 * enclosed by brackets [] replaced by your own identifying information:
 * "Portions Copyright [year] [name of copyright owner]"
 */

import java.lang.annotation.Annotation;

public class Main {
    /**
     * Obtains the specified {@link Annotation} instance on the provided {@link Class},
     * interfaces implemented by the {@link Class} and/or the super-class(es)/super-interface(s)
     * of the {@link Class}.
     * <p>
     * Should the {@link Annotation} not be defined on the above, <code>null</code> is returned.
     *
     * @param onClass                 the {@link Class} on which seaching will take place
     * @param desiredAnnotationClass  the desired {@link Annotation} {@link Class}
     * @param <A>                     the type of the {@link Annotation}
     *
     * @return  the {@link Annotation} or <code>null</code> if not available
     */
    public static <A extends Annotation> A getAnnotation(Class<?> onClass,
            Class<A> desiredAnnotationClass) {
        if (onClass == null || desiredAnnotationClass == null) {
            // when no class or annotation has been provided, we can't locate the desired annotation
            return null;
        } else if (onClass.getClass().equals(Object.class)) {
            // we assume that the object class doesn't have the annotation we want
            return null;
        } else {
            // first check if the annotation is defined directly on the class
            A annotation = onClass.getAnnotation(desiredAnnotationClass);

            if (annotation == null) {
                // look for the annotation on all of the interfaces
                for (Class<?> onInterface : onClass.getInterfaces()) {
                    annotation = getAnnotation(onInterface,
                            desiredAnnotationClass);

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

                // finally look on the super class
                return getAnnotation(onClass.getSuperclass(),
                        desiredAnnotationClass);
            } else {
                return annotation;
            }
        }
    }
}

Related