Mybatis框架-17：多表操作之一对多——分布查询

悠悠 2022-01-21 06:39 259阅读 0赞

# 第一步：建立mapper #

**客户的mapper**

List<Customer> getAllCustomer();

**订单的mapper**

因为这里是根据客户的id进行的查询，所以形参为integer类型

Order getOrderWithCustId(Integer custId);

# 第二步：编写mapper.xml中的sql语句 #

**客户的mapper.xml**

这里同样是查询完客户以后，再讲客户的id作为参数，去订单的mapper.xml中寻找相应的语句进行查询

<resultMap id="allCustomerMap2" type="com.ctbu.domain.Customer">
            <id column="cust_id" property="cust_id"/>
            <result column="cust_name" property="cust_name"/>
            <result column="cust_phone" property="cust_phone"/>
            <result column="cust_profession" property="cust_profession"/>
            <result column="email" property="email"/>
            <collection property="orders" ofType="com.ctbu.domain.Order" javaType="list" select="com.ctbu.mapper.OrderMapper.getOrderWithCustId" column="cust_id"/>
        </resultMap>
    
        <select id="getAllCustomer" resultMap="allCustomerMap2">
            select * from `customer`;
        </select>

**订单的mapper.xml**

<select id="getOrderWithCustId" parameterType="integer" resultType="com.ctbu.domain.Order">
            select * from  `order` where orderCustId=#{id};
        </select>

# 第三步：编写测试类 #

@Test
        public void test7(){
            SqlSession session = MyUtils.openSession();
            CustomerMapper mapper = session.getMapper(CustomerMapper.class);
            List<Customer> allCustomer = mapper.getAllCustomer();
            for (Customer customer : allCustomer) {
                System.out.println(customer);
            }
            session.close();
        }