mybatis useGeneratedKey与keyProperty

<insert id="insert" parameterType="com.mall.pojo.OrderItem" useGeneratedKeys="true" keyProperty="id">
  insert into mmall_order_item (id, user_id, order_no, 
    product_name, product_id, product_image, 
    current_unit_prices, quality, table_price, 
    create_time, update_time)
  values (#{id,jdbcType=INTEGER}, #{userId,jdbcType=INTEGER}, #{orderNo,jdbcType=BIGINT}, 
    #{productName,jdbcType=INTEGER}, #{productId,jdbcType=INTEGER}, #{productImage,jdbcType=VARCHAR}, 
    #{currentUnitPrices,jdbcType=DECIMAL}, #{quality,jdbcType=INTEGER}, #{tablePrice,jdbcType=DECIMAL}, 
    now(), now())
</insert>
将userGeneratedKey值至为true,keyProperty="主键",即可获得插入后的主键id