Mybatis框架-14：多表操作之多对一——分布查询

迷南。 2022-01-23 08:57 229阅读 0赞

# 第一步：建立两张表并建立外键联系 #

我这里是客户与订单的表进行举例

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM4MTk4NDY3_size_16_color_FFFFFF_t_70][]

# 第二步：建立对应关系的映射类（domain） #

customer类

@Data
    public class Customer {
        private Integer cust_id;
        private String cust_name;
        private String cust_profession;
        private String cust_phone;
        private String email;
    
    }

order类

@Data
    public class Order {
        private Integer orderId;
        private String orderName;
        private String orderNum;
        private Customer customer;
    }

# 第三步：编写mapper #

public interface OrderMapper {
      
        public Order getOrderById(Integer id);
    }

# 第四步:编写mapper.xml #

这里相当于是查询完第order之后，再讲order的外键作为参数，传入另外一个mapper.xml中的另外一个语句中进行查询

<resultMap id="orderMap2" type="com.ctbu.domain.Order">
            <result property="orderId" column="orderId"/>
            <result property="orderName" column="orderName"/>
            <result property="orderNum" column="orderNum"/>
    
            <association property="customer" javaType="Customer" select="com.ctbu.mapper.CustomerMapper.getCustomerById" column="orderCustId"/>
        </resultMap>
        <select id="getOrderById" resultMap="orderMap2">
          select * from `order` where  orderId=#{id};
        </select>

# 第五步：测试程序 #

@Test
        public void test5(){
            SqlSession session = MyUtils.openSession();
            OrderMapper mapper = session.getMapper(OrderMapper.class);
            Order order = mapper.getOrderById(1);
            System.out.println(order);
            session.close();
        }

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