MyBatis的每一个查询映射的返回类型都是ResultMap，只是当我们提供的返回类型属性是resultType的时候，MyBatis对自动的给我们把对应的值赋给resultType所指定对象的属性，而当我们提供的返回类型是resultMap的时候，将中列数据复制到对象的相应属性上，可以用于复制查询，两者不能同时用。

1、resultType

返回单个实例

<select id="selectUser" parameterType="int" resultType="User">

select * from user where id = #{id}

</select>

返回List集合

<select id="selectUserAll" resultType="User" > <!-- resultMap="userMap" -->

select * from user

</select>

2、resultMap

简单查询：

<resultMap type="User" id="userMap">

<id column="id" property="id"/>

<result column="name" property="name"/>

</resultMap>

column:数据库中列名称，property:类中属性名称

 

resultMap：适合使用返回值是自定义实体类的情况

resultType：适合使用返回值得数据类型是非自定义的，即jdk的提供的类型

resultMap ： 

映射实体类的数据类型

resultMap的唯一标识

column: 库表的字段名

property： 实体类里的属性名

配置映射文件：

    
    
     
      
      
       
       
       
       
       
       
      
      
      
      select * from person p where p.person_id = #{id}  
      
      select count(*) from person  
      select * from person p where p.person_id= #{id}  
    

实体类Person.

package com.hao947.model; import java.util.Date; public class Person { private Integer personId; private String name; private Integer gender; private String personAddr; private Date birthday; @Override public String toString() { return "Person [personId=" + personId + ", name=" + name + ", gender=" + gender + ", personAddr=" + personAddr + ", birthday=" + birthday + "]"; } }

测试类

public class PersonTest { SqlSessionFactory sqlSessionFactory; @Before public void setUp() throws Exception { // 读取资源流 InputStream in = Resources.getResourceAsStream("sqlMapConfig.xml"); // 初始化session工厂 sqlSessionFactory = new SqlSessionFactoryBuilder().build(in); } @Test public void selectPersonById() { // 创建一个sqlsession SqlSession session = sqlSessionFactory.openSession(); try { Person p = session.selectOne( "com.hao947.sql.mapper.PersonMapper.selectPersonById", 1); System.out.println(p); } finally { session.close(); } } @Test public void selectPersonCount() { // 创建一个sqlsession SqlSession session = sqlSessionFactory.openSession(); try { Integer p = session.selectOne( "com.hao947.sql.mapper.PersonMapper.selectPersonCount"); System.out.println(p); } finally { session.close(); } } @Test public void selectPersonByIdWithMap() { // 创建一个sqlsession SqlSession session = sqlSessionFactory.openSession(); try { Map
    
      map = session.selectOne( "com.hao947.sql.mapper.PersonMapper.selectPersonByIdWithMap",1); System.out.println(map); } finally { session.close(); } } }