ClassUtils.java

package org.quartz.utils;

import java.lang.annotation.Annotation;
import java.util.Arrays;
import java.util.LinkedList;
import java.util.Queue;

public class ClassUtils {

    
    public static boolean isAnnotationPresent(Class<?> clazz, Class<? extends Annotation> a) {
        for (Class<?> c = clazz; c != null; c = c.getSuperclass()) {
            if (c.isAnnotationPresent(a))
                return true;
            if(isAnnotationPresentOnInterfaces(c, a))
                return true;
        }
        return false;
    }

    private static boolean isAnnotationPresentOnInterfaces(Class<?> clazz, Class<? extends Annotation> a) {
        for(Class<?> i : clazz.getInterfaces()) {
            if( i.isAnnotationPresent(a) )
                return true;
            if(isAnnotationPresentOnInterfaces(i, a))
                return true;
        }
        
        return false;
    }

    public static <T extends Annotation> T getAnnotation(Class<?> clazz, Class<T> aClazz) {
        //Check class hierarchy
        for (Class<?> c = clazz; c != null; c = c.getSuperclass()) {
            T anno = c.getAnnotation(aClazz);
            if (anno != null) {
                return anno;
            }
        }

        //Check interfaces (breadth first)
        Queue<Class<?>> q = new LinkedList<Class<?>>();
        q.add(clazz);
        while (!q.isEmpty()) {
            Class<?> c = q.remove();
            if (c != null) {
                if (c.isInterface()) {
                    T anno = c.getAnnotation(aClazz);
                    if (anno != null) {
                        return anno;
                    }
                } else {
                    q.add(c.getSuperclass());
                }
                q.addAll(Arrays.asList(c.getInterfaces()));
            }
        }

        return null;
    }
}