Java Reflection Annotation getAnnotation(final Class c, final Class annClass)

Description

get Annotation

License

Apache License

Declaration

public static <T> T getAnnotation(final Class c, final Class<T> annClass) 

Method Source Code

//package com.java2s;
/**/*from   w ww  .j av  a 2s . c  o m*/
 * Copyright (C) 2010 Olafur Gauti Gudmundsson
 *
 * 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.util.ArrayList;

import java.util.List;

public class Main {
    public static <T> T getAnnotation(final Class c, final Class<T> annClass) {
        final List<T> found = getAnnotations(c, annClass);
        if (found != null && !found.isEmpty()) {
            return found.get(0);
        } else {
            return null;
        }
    }

    /**
     * Returns the (first) instance of the annotation, on the class (or any superclass, or interfaces implemented).
     */
    @SuppressWarnings("unchecked")
    public static <T> List<T> getAnnotations(final Class c, final Class<T> annClass) {
        final List<T> found = new ArrayList<T>();
        // TODO isn't that actually breaking the contract of @Inherited?
        if (c.isAnnotationPresent(annClass)) {
            found.add((T) c.getAnnotation(annClass));
        }

        Class parent = c.getSuperclass();
        while ((parent != null) && (parent != Object.class)) {
            if (parent.isAnnotationPresent(annClass)) {
                found.add((T) parent.getAnnotation(annClass));
            }

            // ...and interfaces that the superclass implements
            for (final Class interfaceClass : parent.getInterfaces()) {
                if (interfaceClass.isAnnotationPresent(annClass)) {
                    found.add((T) interfaceClass.getAnnotation(annClass));
                }
            }

            parent = parent.getSuperclass();
        }

        // ...and all implemented interfaces
        for (final Class interfaceClass : c.getInterfaces()) {
            if (interfaceClass.isAnnotationPresent(annClass)) {
                found.add((T) interfaceClass.getAnnotation(annClass));
            }
        }
        // no annotation found, use the defaults
        return found;
    }
}

Related

1. getAnnotation(Class cls, Annotation... annotations)
2. getAnnotation(Class cls, Method... methods)
3. getAnnotation(Class lookingFor, Annotation[] annotations)
4. getAnnotation(Enum enumConstant, Class annotationClass)
5. getAnnotation(final AnnotatedElement annotatedElement, final Class annotationClass)
6. getAnnotation(final Class annotatedClass, final Class annotationClass)
7. getAnnotation(final Class type, final Class annotation)
8. getAnnotation(final Class reference, final AccessibleObject obj)
9. getAnnotation(final Class annotationClass, final AnnotatedElement... elements)