我在用Springboot构建商城网站后台，请帮我写出商品下单部分Service层代码，只需要写出核心代码即可，不用输出完整代码。
不要用@Autowired（使用@Resource代替）

CREATE TABLE `goods`  (
  `id` bigint(20) UNSIGNED NOT NULL AUTO_INCREMENT,
  `goods_name` varchar(127) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci NOT NULL COMMENT '商品名称',
  `category_id` int(11) NULL DEFAULT 0 COMMENT '商品所属类目ID',
  `brand` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci NULL DEFAULT '0' COMMENT '商品品牌',
  `gallery` varchar(1023) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci NULL DEFAULT '[]' COMMENT '商品宣传图片列表，采用JSON数组格式',
  `brief` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci NULL DEFAULT NULL COMMENT '商品简介',
  `is_on_sale` tinyint(1) NULL DEFAULT 1 COMMENT '是否上架 0为下架 1为上架',
  `sort_order` smallint(4) NULL DEFAULT 100 COMMENT '排序',
  `pic_url` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci NULL DEFAULT NULL COMMENT '商品页面商品图片',
  `type` tinyint(1) NULL DEFAULT 0 COMMENT '商品类型',
  `unit` varchar(31) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci NULL DEFAULT '件' COMMENT '商品单位，例如件、盒',
  `counter_price` decimal(10, 2) NULL DEFAULT 0.00 COMMENT '专柜价格（原价 / 划线价）',
  `retail_price` decimal(10, 2) NULL DEFAULT 100000.00 COMMENT '零售价格（售价 / 未划线价）',
  `detail` text CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci NULL COMMENT '商品详细介绍，是富文本格式',
  `deleted` tinyint(1) NULL DEFAULT 0 COMMENT '逻辑删除 0为正常 1为删除',
  PRIMARY KEY (`id`) USING BTREE,
  INDEX `category_id`(`category_id`) USING BTREE,
  INDEX `brand_id`(`brand`) USING BTREE,
  INDEX `sort_order`(`sort_order`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 23 CHARACTER SET = utf8mb4 COLLATE = utf8mb4_unicode_ci COMMENT = '商品基本信息表' ROW_FORMAT = Dynamic;

CREATE TABLE `goods_category`  (
  `id` bigint(11) NOT NULL AUTO_INCREMENT,
  `category_name` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci NULL DEFAULT NULL COMMENT '商品分类名',
  `order` int(11) NULL DEFAULT NULL COMMENT '排序',
  PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 6 CHARACTER SET = utf8mb4 COLLATE = utf8mb4_unicode_ci ROW_FORMAT = Dynamic;

CREATE TABLE `orders`  (
  `order_id` int(11) NOT NULL AUTO_INCREMENT COMMENT '订单ID',
  `user_id` int(11) NOT NULL COMMENT '用户ID',
  `order_date` date NOT NULL COMMENT '订单日期',
  `order_status` enum('Pending','Processing','Shipped','Delivered','Cancelled') CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci NOT NULL COMMENT '订单状态',
  PRIMARY KEY (`order_id`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8mb4 COLLATE = utf8mb4_unicode_ci ROW_FORMAT = Dynamic;

CREATE TABLE `goods_order_details`  (
  `order_detail_id` int(11) NOT NULL AUTO_INCREMENT COMMENT '订单详情ID',
  `order_id` int(11) NOT NULL COMMENT '订单ID',
  `product_id` int(11) NOT NULL COMMENT '商品ID',
  `product_quantity` int(11) NOT NULL COMMENT '商品数量',
  PRIMARY KEY (`order_detail_id`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8mb4 COLLATE = utf8mb4_unicode_ci ROW_FORMAT = Dynamic;