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package tk.hongkailiu.test.app.util;

import org.apache.log4j.Logger;

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

/**
 * ref. https://github.com/vallourec/zebra/blob/master/src/main/java/com/vallourec/zebra/core/utils/Reflections.java
 *
 * @author Liu
 */
public class ReflectionUtil {

    static Logger logger = Logger.getLogger(ReflectionUtil.class);

    /**
     *
     * * 通过反射, 获得Class定义中声明的泛型参数的类型, 注意泛型必须定义在父类处
     * 如无法找到, 返回Object.class.
     * eg.
     * public UserDao extends HibernateDao of User
     *
     * @param clazz The class to introspect
     * @return the first generic declaration, or Object.class if cannot be determined
     * @param  td
     */

    @SuppressWarnings({"unchecked", "rawtypes"}) public static  Class getClassGenricType(
        final Class clazz) {
        return getClassGenricType(clazz, 0);
    }

    /**
     * 通过反射, 获得Class定义中声明的父类的泛型参数的类型.
     * 如无法找到, 返回Object.class.
     * 
     * 如public UserDao extends HibernateDao of User,Long
     * 
     * @param clazz clazz The class to introspect
     * @param index the Index of the generic ddeclaration,start from 0.
     * @return the index generic declaration, or Object.class if cannot be determined
     */
    @SuppressWarnings("rawtypes") public static Class getClassGenricType(final Class clazz,
        final int index) {

        Type genType = clazz.getGenericSuperclass();

        if (!(genType instanceof ParameterizedType)) {
            logger.warn(clazz.getSimpleName() + "'s superclass not ParameterizedType");
            return Object.class;
        }

        Type[] params = ((ParameterizedType) genType).getActualTypeArguments();

        if (index >= params.length || index < 0) {
            logger.warn(
                "Index: " + index + ", Size of " + clazz.getSimpleName() + "'s Parameterized Type: "
                    + params.length);
            return Object.class;
        }
        if (!(params[index] instanceof Class)) {
            logger.warn(clazz.getSimpleName()
                + " not set the actual class on superclass generic parameter");
            return Object.class;
        }

        return (Class) params[index];
    }
}