Java Reflection Generic Type from Class getGenericArgumentType(Class clazz)

Description

Gets the first generic argument of the given class.

License

Open Source License

Parameter

Parameter	Description
clazz	class from which to extract generic argument

Return

type of generic argument

Declaration

public static Class getGenericArgumentType(Class clazz) 

Method Source Code

//package com.java2s;
/*//from www . j  ava2s  .c  o  m
 * Copyright (c) 2012 Brown Bag Consulting.
 * This file is part of the ExpressUI project.
 * Author: Juan Osuna
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License Version 3
 * as published by the Free Software Foundation with the addition of the
 * following permission added to Section 15 as permitted in Section 7(a):
 * FOR ANY PART OF THE COVERED WORK IN WHICH THE COPYRIGHT IS OWNED BY
 * Brown Bag Consulting, Brown Bag Consulting DISCLAIMS THE WARRANTY OF
 * NON INFRINGEMENT OF THIRD PARTY RIGHTS.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 * The interactive user interfaces in modified source and object code versions
 * of this program must display Appropriate Legal Notices, as required under
 * Section 5 of the GNU Affero General Public License.
 *
 * You can be released from the requirements of the license by purchasing
 * a commercial license. Buying such a license is mandatory as soon as you
 * develop commercial activities involving the ExpressUI software without
 * disclosing the source code of your own applications. These activities
 * include: offering paid services to customers as an ASP, providing
 * services from a web application, shipping ExpressUI with a closed
 * source product.
 *
 * For more information, please contact Brown Bag Consulting at this
 * address: juan@brownbagconsulting.com.
 */

import java.lang.reflect.*;

public class Main {
    /**
     * Gets the first generic argument of the given class.
     *
     * @param clazz class from which to extract generic argument
     * @return type of generic argument
     */
    public static Class getGenericArgumentType(Class clazz) {
        return getGenericArgumentType(clazz, 0);
    }

    /**
     * Gets a generic argument of the given class, based on arg index.
     *
     * @param clazz    class from which to extract generic argument
     * @param argIndex index of the declared argument type
     * @return type of generic argument
     */
    public static Class getGenericArgumentType(Class clazz, int argIndex) {
        Type type = clazz.getGenericSuperclass();

        if (type != null && type instanceof ParameterizedType) {
            if (((ParameterizedType) type).getActualTypeArguments()[argIndex] instanceof Class) {
                return (Class) ((ParameterizedType) type).getActualTypeArguments()[argIndex];
            } else {
                return null;
            }
        } else {
            if (!(type instanceof Class) || type.equals(Object.class)) {
                return null;
            } else {
                return getGenericArgumentType((Class) type, argIndex);
            }
        }
    }
}

Related

1. getGenericArgumentType(Class currentClass, Class genericSuperClass, int argumentIndex)
2. getGenericClass(Class clazz)
3. getGenericClass(Class clazz)
4. getGenericClass(Class clazz)