mybatis: 多对多通过注解查询数据

多对多通过注解查询数据

案例: 获取订单的详细信息

1.实体类:

public class Category {
    private int id;
    private String name;
    List<Product> products;
}

public class Product {
    private int id;
    private String name;
    private float price;
    private Category category;
}

public class Order {  //订单
    private int id;
    private String code;
    List<OrderItem> orderItems;
}

public class OrderItem {  //订单物品
    private int id;
    private int number;
    private Order order;
    private Product product;
}

2.关系分析:

订单1----订单物品n----产品n----分类1

3.dao层:

public interface OrderMapper {
    @Select("select * from order_")
     @Results({
            @Result(property = "id", column = "id"),
            @Result(property = "orderItems", javaType = List.class, column = "id", 
                    many = @Many(select = "com.how2java.mapper.OrderItemMapper.listByOrder"))
            })      
    public List<Order> list();
     
}

public interface OrderItemMapper {
     
    @Select(" select * from order_item_ where oid = #{oid}")
    @Results({ 
        @Result(property="product",column="pid",one=@One(select="com.how2java.mapper.ProductMapper.get")) 
    }) 
    public List<OrderItem> listByOrder(int oid);
}

public interface ProductMapper {
     
    @Select("select * from product_ where id = #{id}")
    public Product get(int id);
}

4.效果图: