ClassUtils.java

package org.resthub.common.util;

import org.springframework.aop.support.AopUtils;

import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;

/**
 * Utility class to work with classes.
 */
public abstract class ClassUtils {

    /**
     * Private constructor to prevent instantiation.
     */
    private ClassUtils() {

    }

    public static Class<?> getGenericTypeFromBean(Object object) {
        Class<?> clazz = object.getClass();

        if (AopUtils.isAopProxy(object)) {
            clazz = AopUtils.getTargetClass(object);
        }
        return getGenericType(clazz);
    }

    public static Class<?> getGenericType(Class<?> clazz) {

        return getGenericType(clazz, 0);
    }

    /**
     * Returns the generic type with the given index from the given {@link Class}.
     * Scan all base classes until finding a generic type.
     * 
     * @param clazz Class where seeking the generic type
     * @param index index of the generic type to find in the actual type array
     * @return the generic type
     */
    public static Class<?> getGenericType(Class<?> clazz, int index) {

        Type genericSuperclass = clazz.getGenericSuperclass();

        if (genericSuperclass == null) {
            return null;
        }

        Class<?> effectiveClass = clazz;
        while (!(genericSuperclass instanceof ParameterizedType)) {
            effectiveClass = effectiveClass.getSuperclass();
            genericSuperclass = effectiveClass.getGenericSuperclass();

            if (effectiveClass.equals(Object.class)) {
                return null;
            }
        }
        return (Class<?>) ((ParameterizedType) genericSuperclass).getActualTypeArguments()[index];

    }

}