Java Reflection Annotation getAnnotationValue(@Nonnull Class cls, @Nonnull Class annotation, V def)

License

Parameter

Declaration

public static <V, A extends Annotation> V getAnnotationValue(@Nonnull Class<?> cls,
        @Nonnull Class<A> annotation, V def) 

Method Source Code

//package com.java2s;
/*/*from  www  . java  2  s.  c  o  m*/
 * Copyright 2016-2017 Daniel Siviter
 *
 * 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.Field;

import java.lang.reflect.Method;
import java.lang.reflect.Modifier;

import javax.annotation.Nonnull;

public class Main {
    /**
     * 
     * @param cls
     * @param annotation
     * @param def
     * @return
     */
    public static <V, A extends Annotation> V getAnnotationValue(@Nonnull Class<?> cls,
            @Nonnull Class<A> annotation, V def) {
        final A a = getAnnotation(cls, annotation);
        return a != null ? get(a, "value") : def;
    }

    /**
     * 
     * @param obj
     * @param annotation
     * @param def
     * @return
     */
    public static <V, A extends Annotation> V getAnnotationValue(@Nonnull Object obj, @Nonnull Class<A> annotation,
            V def) {
        return getAnnotationValue(obj.getClass(), annotation, def);
    }

    /**
     * 
     * @param cls
     * @param annotation
     * @return
     */
    public static <V, A extends Annotation> V getAnnotationValue(@Nonnull Class<?> cls,
            @Nonnull Class<A> annotation) {
        return getAnnotationValue(cls, annotation, null);
    }

    /**
     * 
     * @param obj
     * @return
     */
    public static <V, A extends Annotation> V getAnnotationValue(Object obj, Class<A> annotation) {
        return getAnnotationValue(obj.getClass(), annotation);
    }

    /**
     * 
     * @param cls
     * @param annotation
     * @return
     */
    public static <A extends Annotation> A getAnnotation(@Nonnull Class<?> cls, @Nonnull Class<A> annotation) {
        return annotation.cast(cls.getAnnotation(annotation));
    }

    /**
     * 
     * @param obj
     * @param annotation
     * @return
     */
    public static <A extends Annotation> A getAnnotation(@Nonnull Object obj, @Nonnull Class<A> annotation) {
        return getAnnotation(obj.getClass(), annotation);
    }

    /**
     * 
     * @param source
     * @param name
     * @return
     */
    public static <T> T get(@Nonnull Object source, @Nonnull String name) {
        return get(source, name, null);
    }

    /**
     * 
     * @param source
     * @param name
     * @param type
     * @return
     */
    @SuppressWarnings("unchecked")
    public static <T> T get(@Nonnull Object source, @Nonnull String name, Class<T> type) {
        try {
            final Field field = findField(source.getClass(), name, type);
            if (field == null) {
                throw new IllegalArgumentException(
                        String.format("Unable to find '%s' on '%s'!", name, source.getClass()));
            }
            setAccessible(field);
            return (T) field.get(source);
        } catch (IllegalAccessException ex) {
            throw new IllegalStateException(
                    String.format("Unexpected reflection exception - %s", ex.getClass().getName()), ex);
        }
    }

    /**
     * 
     * @param source
     * @param name
     * @param type
     * @return
     */
    @SuppressWarnings("unchecked")
    public static <T> T get(@Nonnull Class<?> sourceCls, @Nonnull String name, Class<T> type) {
        try {
            final Field field = findField(sourceCls, name, type);
            if (field == null) {
                throw new IllegalArgumentException(String.format("Unable to find '%s' on '%s'!", name, sourceCls));
            }
            setAccessible(field);
            return (T) field.get(null);
        } catch (IllegalAccessException ex) {
            throw new IllegalStateException(
                    String.format("Unexpected reflection exception - %s", ex.getClass().getName()), ex);
        }
    }

    /**
     * 
     * @param clazz
     * @param name
     * @param type
     * @return
     */
    public static Field findField(@Nonnull Class<?> clazz, @Nonnull String name, Class<?> type) {
        Class<?> searchType = clazz;
        while (!Object.class.equals(searchType) && searchType != null) {
            for (Field field : searchType.getDeclaredFields()) {
                if (name.equals(field.getName()) && (type == null || type.equals(field.getType()))) {
                    return field;
                }
            }
            searchType = searchType.getSuperclass();
        }
        return null;
    }

    /**
     * 
     * @param field
     */
    public static void setAccessible(@Nonnull Field field) {
        if ((!Modifier.isPublic(field.getModifiers())
                || !Modifier.isPublic(field.getDeclaringClass().getModifiers())
                || Modifier.isFinal(field.getModifiers())) && !field.isAccessible()) {
            field.setAccessible(true);
        }
    }

    /**
     * 
     * @param method
     */
    public static void setAccessible(@Nonnull Method method) {
        if ((!Modifier.isPublic(method.getModifiers())
                || !Modifier.isPublic(method.getDeclaringClass().getModifiers())
                || Modifier.isFinal(method.getModifiers())) && !method.isAccessible()) {
            method.setAccessible(true);
        }
    }
}

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