Java Reflection Generic Type getGenericType(Object target)

Description

get Generic Type

License

Open Source License

Parameter

Parameter	Description
target	The target to get the generic class of
T	The generic class type

Return

The generic class

Declaration

public static <T> Class<T> getGenericType(Object target) 

Method Source Code

//package com.java2s;
/**/*from   w w w .  j  a v  a 2 s  . com*/
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see http://www.gnu.org/licenses/.
 */

import java.lang.reflect.*;

public class Main {
    /**
     * @param target The target to get the generic class of
     * @param <T>    The generic class type
     * @return The generic class
     */
    public static <T> Class<T> getGenericType(Object target) {
        return getGenericType(target, 0);
    }

    /**
     * @param target The target to get the generic class of
     * @param index  The index the generic class is declared at
     * @param <T>    The generic class type
     * @return The generic class
     */
    public static <T> Class<T> getGenericType(Object target, int index) {
        Class<?> targetClass = target instanceof Class ? (Class<?>) target : target.getClass();
        return getGenericType(targetClass, index);
    }

    private static <T> Class<T> getGenericType(Class<?> targetClass, int index) {

        // check targetClass first
        Type type = targetClass.getGenericSuperclass();
        if (type instanceof ParameterizedType) {
            return extractGenericType((ParameterizedType) type, index);
        }

        if (type == null) {
            // targetClass is Object or primitive type
            return null;
        }

        // check implemented interfaces
        Type[] interfaceTypes = targetClass.getGenericInterfaces();
        for (Type interfaceType : interfaceTypes) {
            if (interfaceType instanceof ParameterizedType) {
                return extractGenericType((ParameterizedType) interfaceType, index);
            }
        }

        // finally check the superclass
        return getGenericType(targetClass.getSuperclass(), index);
    }

    @SuppressWarnings("unchecked")
    private static <T> Class<T> extractGenericType(ParameterizedType parameterizedType, int index) {
        Type[] actualTypeArguments = parameterizedType.getActualTypeArguments();
        Type actualTypeArgument = actualTypeArguments[index];
        return (Class<T>) actualTypeArgument;
    }
}

Related

1. getGenericString(AccessibleObject ao)
2. getGenericSuperType(Type t)
3. getGenericType(@Nullable Type genericType)
4. getGenericType(Member member, int index)
5. getGenericType(Method setter)
6. getGenericType(Type genType, int index)
7. getGenericType(Type t, int index)
8. getGenericType(Type type)
9. getGenericTypeArguments(Method m, int i)