Java Reflection Annotation getAnnotation(Class cl, Object o)

Description

Looks for the annotation specified on the given object.

License

Apache License

Parameter

Parameter	Description
cl	The annotation class to look for.
o	The object to parse.
T	The annotation type.

Return

The (possibly null) annotation instance.

Declaration

public static <T extends Annotation> T getAnnotation(Class<T> cl, Object o) 

Method Source Code

//package com.java2s;
/**************************************************************************
 *
 * Gluewine Utility Module/*from   w  w  w .  ja  v a 2 s  .  c  om*/
 *
 * Copyright (C) 2013 FKS bvba               http://www.fks.be/
 *
 * 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.lang.reflect.Method;

public class Main {
    /**
     * Looks for the annotation specified on the given object. Remark that if
     * the annotation is not @Inherited, the call is only dispatched to the
     * object's class and all its interfaces. Not to its superclasses.
     *
     * If no such annotation could be found, null is returned.
     *
     * @param cl The annotation class to look for.
     * @param o The object to parse.
     * @param <T> The annotation type.
     * @return The (possibly null) annotation instance.
     */
    public static <T extends Annotation> T getAnnotation(Class<T> cl, Object o) {
        return getAnnotation(cl, o.getClass());
    }

    /**
     * Looks for the annotation specified in the given class. All the interfaces
     * the class implements are also being searched.
     *
     * @param ann The annotation to look for.
     * @param cl The class to process.
     * @param <T> The annotation type.
     * @return The (possibly null) annotation.
     */
    public static <T extends Annotation> T getAnnotation(Class<T> ann, Class<?> cl) {
        T res = null;

        res = cl.getAnnotation(ann);
        if (res == null) {
            Class<?>[] inter = cl.getInterfaces();
            for (int i = 0; i < inter.length && res == null; i++)
                res = inter[i].getAnnotation(ann);
        }

        return res;
    }

    /**
     * Looks for the annotation given in the method specified. If the annotation is
     * not found on the object, all the superclasses and interfaces are parsed as well.
     *
     * @param ann The annotation to look for.
     * @param m The method being inspected.
     * @param o The object owning the method.
     * @param <T> The annotation type.
     * @return The (possibly null) annotation.
     */
    public static <T extends Annotation> T getAnnotation(Class<T> ann, Method m, Object o) {
        T res = null;

        res = m.getAnnotation(ann);
        if (res == null) {
            Class<?> cl = o.getClass().getSuperclass();
            while (cl != null && res == null) {
                try {
                    Method m2 = cl.getMethod(m.getName(), m.getParameterTypes());
                    res = m2.getAnnotation(ann);
                } catch (Throwable e) {
                    // Ignore it, as this is bound to happen.
                }

                Class<?>[] interf = cl.getInterfaces();
                for (int i = 0; i < interf.length && res == null; i++) {
                    try {
                        Method m2 = interf[i].getMethod(m.getName(), m.getParameterTypes());
                        res = m2.getAnnotation(ann);
                    } catch (Throwable e) {
                        // Ignore it, as this is bound to happen.
                    }
                }
                cl = cl.getSuperclass();
            }
        }

        return res;
    }
}

Related

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2. getAnnotation(Class a, Class c)
3. getAnnotation(Class annotation, Class ownerClass, Method method)
4. getAnnotation(Class annotationClass, Class cls)
5. getAnnotation(Class annotationType, AnnotatedElement... objects)
6. getAnnotation(Class clazz, Method method, int parameterIndex)
7. getAnnotation(Class cls, Annotation... annotations)
8. getAnnotation(Class cls, Method... methods)
9. getAnnotation(Class lookingFor, Annotation[] annotations)