GenericTypes.java

package core.framework.impl.reflect;

import core.framework.api.util.Exceptions;

import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.List;
import java.util.Map;
import java.util.Optional;

/**
 * @author neo
 */
public final class GenericTypes {
    public static Class<?> rawClass(Type type) {
        if (type instanceof Class) {
            return (Class<?>) type;
        } else if (type instanceof ParameterizedType) {
            return (Class<?>) ((ParameterizedType) type).getRawType();
        } else {
            throw Exceptions.error("unsupported type, type={}", type);
        }
    }

    public static boolean isList(Type type) {
        return List.class.isAssignableFrom(rawClass(type));
    }

    public static boolean isGenericList(Type type) {
        if (type instanceof ParameterizedType) {
            Class<?> rawClass = (Class<?>) ((ParameterizedType) type).getRawType();
            return List.class.isAssignableFrom(rawClass)
                && ((ParameterizedType) type).getActualTypeArguments()[0] instanceof Class;
        }
        return false;
    }

    public static Class<?> listValueClass(Type type) {
        return (Class<?>) ((ParameterizedType) type).getActualTypeArguments()[0];
    }

    public static boolean isOptional(Type type) {
        return Optional.class.isAssignableFrom(rawClass(type));
    }

    public static boolean isGenericOptional(Type type) {
        if (type instanceof ParameterizedType) {
            Class<?> rawClass = (Class<?>) ((ParameterizedType) type).getRawType();
            return Optional.class.isAssignableFrom(rawClass)
                && ((ParameterizedType) type).getActualTypeArguments()[0] instanceof Class;
        }
        return false;
    }

    public static Class<?> optionalValueClass(Type type) {
        return (Class<?>) ((ParameterizedType) type).getActualTypeArguments()[0];
    }

    public static boolean isMap(Type type) {
        return Map.class.isAssignableFrom(rawClass(type));
    }

    public static boolean isGenericStringMap(Type type) {
        if (type instanceof ParameterizedType) {
            Type keyType = ((ParameterizedType) type).getActualTypeArguments()[0];
            if (!(keyType instanceof Class)) return false;
            Class<?> keyClass = (Class<?>) keyType;
            return String.class.equals(keyClass)
                && ((ParameterizedType) type).getActualTypeArguments()[1] instanceof Class;
        }
        return false;
    }

    public static Class<?> mapValueClass(Type type) {
        return (Class<?>) ((ParameterizedType) type).getActualTypeArguments()[1];
    }
}