mybatisplus多张关联表新增

以下是Mybatis Plus多张关联表新增的示例代码：

1.定义实体类

public class Order implements Serializable {
    private static final long serialVersionUID = 1L;
    private Long id;
    private String orderNo;
    private Long userId;
    private User user;
    private List<OrderItem> orderItems;
    // 省略getter和setter方法
}

public class OrderItem implements Serializable {
    private static final long serialVersionUID = 1L;
    private Long id;
    private Long orderId;
    private Long productId;
    private Integer quantity;
    private Product product;
    // 省略getter和setter方法
}

public class Product implements Serializable {
    private static final long serialVersionUID = 1L;
    private Long id;
    private String name;
    private BigDecimal price;
    // 省略getter和setter方法
}

public class User implements Serializable {
    private static final long serialVersionUID = 1L;
    private Long id;
    private String username;
    private String password;
    // 省略getter和setter方法
}

2.定义Mapper接口

public interface OrderMapper extends BaseMapper<Order> {
    int insertOrder(Order order);
}

public interface OrderItemMapper extends BaseMapper<OrderItem> {
    int insertOrderItem(OrderItem orderItem);
}

public interface ProductMapper extends BaseMapper<Product> {
    // 省略其他方法
}

public interface UserMapper extends BaseMapper<User> {
    // 省略其他方法
}

3.定义Mapper.xml文件

<!-- OrderMapper.xml -->
<mapper namespace="com.example.mapper.OrderMapper">
    <insert id="insertOrder" parameterType="com.example.entity.Order">
        insert into `order` (order_no, user_id) values (#{orderNo}, #{userId})
    </insert>
</mapper>

<!-- OrderItemMapper.xml -->
<mapper namespace="com.example.mapper.OrderItemMapper">
    <insert id="insertOrderItem" parameterType="com.example.entity.OrderItem">
        insert into order_item (order_id, product_id, quantity) values (#{orderId}, #{productId}, #{quantity})
    </insert>
</mapper>

4.定义Service层

@Service
public class OrderServiceImpl implements OrderService {
    @Autowired
    private OrderMapper orderMapper;
    @Autowired
    private OrderItemMapper orderItemMapper;
    @Autowired
    private ProductMapper productMapper;
    @Autowired
    private UserMapper userMapper;

    @Override
    @Transactional
    public void addOrder(Order order) {
        // 插入订单
        orderMapper.insertOrder(order);
        Long orderId = order.getId();
        // 插入订单项
        List<OrderItem> orderItems = order.getOrderItems();
        for (OrderItem orderItem : orderItems) {
            orderItem.setOrderId(orderId);
            orderItemMapper.insertOrderItem(orderItem);
        }
    }
}

5.调用Service层方法进行新增操作

Order order = new Order();
order.setOrderNo("202201010001");
order.setUserId(1L);
User user = userMapper.selectById(order.getUserId());
order.setUser(user);
List<OrderItem> orderItems = new ArrayList<>();
OrderItem orderItem1 = new OrderItem();
orderItem1.setProductId(1L);
orderItem1.setQuantity(2);
Product product1 = productMapper.selectById(orderItem1.getProductId());
orderItem1.setProduct(product1);
orderItems.add(orderItem1);
OrderItem orderItem2 = new OrderItem();
orderItem2.setProductId(2L);
orderItem2.setQuantity(1);
Product product2 = productMapper.selectById(orderItem2.getProductId());
orderItem2.setProduct(product2);
orderItems.add(orderItem2);
order.setOrderItems(orderItems);
orderService.addOrder(order);