Java Reflection Annotation getAnnotation( final Method method, final Class annotationClass)

Description

get Annotation

License

Open Source License

Declaration

public static <T extends Annotation> T getAnnotation(
            final Method method, final Class<T> annotationClass) 

Method Source Code

//package com.java2s;
/*******************************************************************************
 * Copyright (c) 2012 IBM Corporation./*from w  ww  .  j a v a2 s  .  c o  m*/
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * and Eclipse Distribution License v. 1.0 which accompanies this distribution.
 *   
 * The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
 * and the Eclipse Distribution License is available at
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * Contributors:
 *
 *      Russell Boykin      - initial API and implementation
 *      Alberto Giammaria   - initial API and implementation
 *      Chris Peters         - initial API and implementation
 *      Gianluca Bernardini   - initial API and implementation
 *******************************************************************************/

import java.lang.annotation.Annotation;
import java.lang.reflect.Method;

public class Main {
    public static <T extends Annotation> T getAnnotation(
            final Method method, final Class<T> annotationClass) {
        // First, try method for annotation

        final T annotation = method.getAnnotation(annotationClass);

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

        final Class<?> declaringClass = method.getDeclaringClass();

        // Second, try superclass hierarchy for method annotation

        Class<?> currentSuperClass = declaringClass.getSuperclass();

        while (currentSuperClass != null) {
            try {
                final Method superClassMethod = currentSuperClass
                        .getMethod(method.getName(),
                                method.getParameterTypes());

                final T superClassMethodAnnotation = superClassMethod
                        .getAnnotation(annotationClass);

                if (superClassMethodAnnotation != null) {
                    return superClassMethodAnnotation;
                }
            } catch (final Exception exception) {
                // Ignore and fall through to code below
            }

            currentSuperClass = currentSuperClass.getSuperclass();
        }

        // Third, try superclass' interface hierarchy for method annotation

        Class<?> currentClass = declaringClass;

        do {
            final Class<?>[] interfaces = currentClass.getInterfaces();

            for (final Class<?> interfac : interfaces) {
                final T interfaceMethodAnnotation = getRecursiveInterfaceMethodAnnotation(
                        interfac, method, annotationClass);

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

            currentClass = currentClass.getSuperclass();
        } while (currentClass != null);

        return null;
    }

    private static <T extends Annotation> T getRecursiveInterfaceMethodAnnotation(
            final Class<?> interfac, final Method method,
            final Class<T> annotationClass) {
        try {
            final Method interfaceMethod = interfac.getMethod(
                    method.getName(), method.getParameterTypes());

            final T interfaceMethodAnnotation = interfaceMethod
                    .getAnnotation(annotationClass);

            if (interfaceMethodAnnotation != null) {
                return interfaceMethodAnnotation;
            }
        } catch (final Exception exception) {
            // Ignore and fall through to code below
        }

        final Class<?>[] superInterfaces = interfac.getInterfaces();

        for (final Class<?> superInterface : superInterfaces) {
            final T interfaceMethodAnnotation = getRecursiveInterfaceMethodAnnotation(
                    superInterface, method, annotationClass);

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

        return null;
    }
}

Related

1. getAnnotation( final AnnotatedElement anElement, final Class annotationClass)
2. getAnnotation(@Nonnull Annotation[] annotations, @Nonnull Class annotation)
3. getAnnotation(@Nonnull Class cls, @Nonnull Class annotation)
4. getAnnotation(AnnotatedElement ae, Class annotationType)
5. getAnnotation(AnnotatedElement aobj, Class aClass)