GenericUtil.java

package com.miragesql.miragesql.util;


import java.lang.reflect.Array;
import java.lang.reflect.GenericArrayType;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.lang.reflect.WildcardType;
import java.util.List;

public abstract class GenericUtil {

    protected GenericUtil() {
    }

    public static boolean isTypeOf(final Type type, final Class<?> clazz) {
        if (Class.class.isInstance(type)) {
            return clazz.isAssignableFrom(Class.class.cast(type));
        }
        if (ParameterizedType.class.isInstance(type)) {
            final ParameterizedType parameterizedType = ParameterizedType.class
                    .cast(type);
            return isTypeOf(parameterizedType.getRawType(), clazz);
        }
        return false;
    }

    public static Class<?> getRawClass(final Type type) {
        if (Class.class.isInstance(type)) {
            return Class.class.cast(type);
        }
        if (ParameterizedType.class.isInstance(type)) {
            final ParameterizedType parameterizedType = ParameterizedType.class
                    .cast(type);
            return getRawClass(parameterizedType.getRawType());
        }
        if (WildcardType.class.isInstance(type)) {
            final WildcardType wildcardType = WildcardType.class.cast(type);
            final Type[] types = wildcardType.getUpperBounds();
            return getRawClass(types[0]);
        }
        if (GenericArrayType.class.isInstance(type)) {
            final GenericArrayType genericArrayType = GenericArrayType.class
                    .cast(type);
            final Class<?> rawClass = getRawClass(genericArrayType
                    .getGenericComponentType());
            return Array.newInstance(rawClass, 0).getClass();
        }
        return null;
    }

    public static Type[] getGenericParameter(final Type type) {
        if (ParameterizedType.class.isInstance(type)) {
            return ParameterizedType.class.cast(type).getActualTypeArguments();
        }
        if (GenericArrayType.class.isInstance(type)) {
            return getGenericParameter(GenericArrayType.class.cast(type)
                    .getGenericComponentType());
        }
        return null;
    }

    public static Type getGenericParameter(final Type type, final int index) {
        if (!ParameterizedType.class.isInstance(type)) {
            return null;
        }
        final Type[] genericParameter = getGenericParameter(type);
        if (genericParameter == null) {
            return null;
        }
        return genericParameter[index];
    }


    public static Type getElementTypeOfList(final Type type) {
        if (!isTypeOf(type, List.class)) {
            return null;
        }
        return getGenericParameter(type, 0);
    }

}