Java Reflection Annotation Find findAnnotation(Class clazz, Class annotationType)

License

Declaration

public static <A extends Annotation> A findAnnotation(Class<?> clazz, Class<A> annotationType) 

Method Source Code

//package com.java2s;
/*//from  ww  w .  java2  s  .c  o m
 * 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;

import java.util.HashSet;

import java.util.Set;

public class Main {
    public static <A extends Annotation> A findAnnotation(Class<?> clazz, Class<A> annotationType) {
        A annotation = clazz.getAnnotation(annotationType);
        if (annotation != null) {
            return annotation;
        }
        for (Class<?> ifc : clazz.getInterfaces()) {
            annotation = findAnnotation(ifc, annotationType);
            if (annotation != null) {
                return annotation;
            }
        }
        Class<?> superClass = clazz.getSuperclass();
        if (superClass == null || superClass == Object.class) {
            return null;
        }
        return findAnnotation(superClass, annotationType);
    }

    /**
     * Return all interfaces that are implemented by this class, traversing
     * super classes and super interfaces.
     * 
     * @param c
     * @return Set of classes. May be empty but not null.
     */
    public static Set<Class<?>> getInterfaces(Class<?> c) {
        Class<?> interfaces[] = c.getInterfaces();
        Set<Class<?>> classes = new HashSet<Class<?>>();
        if (interfaces == null)
            return classes;
        addAll(classes, interfaces);
        for (Class<?> cl : interfaces) {
            classes.addAll(getInterfaces(cl));
        }
        Class<?> superClass = c.getSuperclass();
        if (superClass != null) {
            classes.addAll(getInterfaces(superClass));
        }
        return classes;
    }

    /**
     * Adds elements of an array to a set. The JRE 1.5 does include a similar
     * method in the Collections class, but that breaks GWT-SL 1.4
     * compatibility.
     * 
     * @param set
     * @param elements
     */
    public static void addAll(Set<Class<?>> set, Class<?>[] elements) {
        for (Class<?> element : elements)
            set.add(element);
    }
}

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