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mybatis typeAlias（别名）使用和resultMap使用

2024-08-17 14:32:49   217人阅读

 1、MyBatis提供的typeAlias

技术分享

技术分享

 

 2、定义自定义类型的别名

 定义自定义类型的别名

1.在mybatis-config.xml中增加

1   <typeAliases>
2       <typeAlias alias="user" type="cn.itcast.pojo.User"/>
3   </typeAliases>

2.在UserMapper.xml中使用别名 resultType="user"

1 <select id="loadUserById" parameterType="integer" resultType="user">
2       select * from user where id = #{id}
3  </select>

 

 

3、resultMap使用

1.创建person表

1   create table person(id int primary key,user_name varchar(50),age int,address varchar(150));
2   desc person;
3   insert into person values(1,’laozhao’,35,’haidian’);

2.创建person.java

 1 public class Person {
 2
 3   private Integer id;
 5   private String userName;
 7   private Integer age;
 9   private String address;
10 
11   set get ...
12 
13 }

3.创建PersonMapper.xml

1 <mapper namespace="cn.itcast.dao.PersonMapper">
2   <select id="loadPersonById" parameterType="integer" resultType="person">
3       select * from person where id = #{id}
4   </select>
5 </mapper>

4.修改mybatis-config.xml,增加person相关信息

1 <typeAliases>
2     <typeAlias alias="person" type="cn.itcast.pojo.Person"/>
3 </typeAliases>
4 <mapper resource="cn/itcast/dao/PersonMapper.xml"/>

5.创建测试类TestPerson

1 @Test
2 public void testloadPersonById(){
3 
4     PersonMapper personMapper = sqlSession.getMapper(PersonMapper.class);
5     Person person = sqlSession.selectOne("cn.itcast.dao.PersonMapper.loadPersonById", 1);
6     System.out.println(person);
7 }

如何在javabean属性和表字段不一致的情况下正常取值？

 

方式一：查询语句中指定别名

1 <select id="loadPersonById2" parameterType="integer" resultType="person">
2 
3 　　select id,user_name as userName,age,address from person where id = #{id}
4 
5 </select>

方式二、使用resultMap标签

 1 <resultMap type="person" id="personMap">
 2 
 3   <result property=“userName" column="user_name"/>
 4 
 5 </resultMap>
 6 
 7 <select id="loadPersonById3" parameterType="integer" resultMap="personMap">
 8 
 9 　　select * from person where id = #{id}
10 
11 </select>

 

resultMap的使用  映射一对多、多对一

技术分享

 

1.创建订单表orders

1  create table orders(id int primary key,pid int,num varchar(12),name varchar(150),price double(10,2));
2 
3  desc orders;
4 
5  insert  orders values(1,1,‘n101‘,‘shouji‘,1342.23);
6 
7  insert  orders values(2,1,‘d102‘,‘diannao‘,8766.74);
8 
9  insert  orders values(3,1,‘p103‘,‘pingban‘,3342.53);

2.创建orders.java

 1  public class Orders {
 2 
 3   private Integer id;
 4 
 5   private String num;
 6 
 7   private String name;
 8 
 9   private Double price;
10 
11   private Person person;
12 
13   get set ...
14 
15 }

3.创建OrdersMapper.xml

 1 <mapper namespace="cn.itcast.dao.OrdersMapper">
 2 
 3   <resultMap type="orders" id="ordersMap">
 4 
 5  　　 <result property="num" column="num"/>
 6 
 7   　　<result property="name" column="name"/>
 8 
 9   　　<association property="person" javaType="person" >
10 
11 　　  　　<result property="name" column="user_name"/>
12 
13  　　 　　<result property="address" column="address"/>
14 
15   　　</association>
16 
17   </resultMap>
18 
19   <select id="loadOrdersById" parameterType="integer" resultMap="ordersMap">
20 
21   select a.*,b.* from orders a,person b where a.pid=b.id and a.id = #{id}
22 
23   </select>
24 
25 </mapper>

4.修改mybatis-config.xml，增加

1 <typeAlias alias="orders" type="cn.itcast.pojo.Orders"/>
2 <typeAlias alias="persion" type="cn.itcast.pojo.Persion"/>
3 <mapper resource="cn/itcast/dao/OrdersMapper.xml"/>

5.创建TestOrders

 1 public class TestOrders {
 2 
 3   @Test
 4 
 5   public void loadOrdersById(){
 6 
 7   Orders o = sqlSession.selectOne("cn.itcast.dao.OrdersMapper.loadOrdersById", 1);
 8 
 9   System.out.println("num:"+o.getNum() + ",name:" + o.getName() + ",personName:"
10 
11   + o.getPerson().getName() + ",address:" + o.getPerson().getAddress());
12 
13   }
14 
15 }

技术分享

1.在Person.java中增加对应订单的list

 1   private List<Orders> ordersList = new ArrayList<Orders>();
 2 
 3   public List<Orders> getOrdersList() {
 4 
 5   return ordersList;
 6 
 7   }
 8 
 9   public void setOrdersList(List<Orders> ordersList) {
10 
11   this.ordersList = ordersList;
12 
13   }

2.在PersonMapper.xml中增加查询

 1 <resultMap type="person" id="personMap2">
 2 
 3  　<result property="name" column="user_name"/>

 4 　　　　<!--配置orderList属性，并制定类型为orders-->
 5   <collection property="ordersList" javaType="orders">
 6 
 7   　　　　<result property="name" column="name"/>
 8 
 9  　　　　 <result property="price" column="price"/>
10 
11   　　　　<result property="num" column="num"/>
12 
13   </collection>
14 
15  </resultMap>
16 
17 <select id="loadPersonById4" parameterType="integer" resultMap="personMap2">
18 
19   select a.*,b.* from person a,orders b where a.id=b.pid and a.id = #{id}
20 
21 </select>

4. TestPerson中增加方法

 1 @Test
 2 
 3   public void loadPersonById4(){
 4 
 5 
 6    Person person = sqlSession.selectOne("cn.itcast.dao.PersonMapper.loadPersonById4", 1);
 7 
 8    System.out.println(person.getName() + "  " + person.getOrdersList().size());
11 
12    for(Orders o: person.getOrdersList()){
13 
14   　　　　 System.out.println(o.getName() + "   " + o.getPrice() + "  " + o.getNum());
15 
16   }
17 
18   }

 

mybatis typeAlias（别名）使用和resultMap使用


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