第一步：建立mapper

客户的mapper

[code]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

[code]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

[code]<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

[code]<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

[code]@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();
}