4.4 MyBatis_映射文件_结果（resultType）

ゞ浴缸里的玫瑰 2022-05-30 23:59 169阅读 0赞

来源于：http://www.cnblogs.com/pjfmeng/p/7688172.html

resultType是sql映射文件中定义返回值类型，返回值有基本类型，对象类型，List类型，Map类型等。现总结一下再解释

## 总结： ##

resultType:

1.  基本类型 ：resultType=基本类型
2.  List类型：   resultType=List中元素的类型
3.  Map类型    单条记录：resultType =map  
                        多条记录：resultType =Map中value的类型

### 1、对象类型 ###

对于对象类型resultType直接写对象的全类名就可以了

实例：

hotelMapper接口

package com.pjf.mybatis.dao;
    
    import com.pjf.mybatis.po.Hotel;
    
    public interface HotelMapper {
        //返回值类型为Hotel
        public Hotel getHotel(Integer i);

HotelMapper.xml

<?xml version="1.0" encoding="UTF-8" ?>
    <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
    <mapper namespace="com.pjf.mybatis.dao.HotelMapper">
        
        <select id="getHotel" resultType="com.pjf.mybatis.po.Hotel">
            select * from hotel
            where
            id=#{id}
        </select>
    </mapper

测试类：

package com.pjf.mybatis;
    
    import java.io.IOException;
    import java.io.InputStream;import org.apache.ibatis.io.Resources;
    import org.apache.ibatis.session.SqlSession;
    import org.apache.ibatis.session.SqlSessionFactory;
    import org.apache.ibatis.session.SqlSessionFactoryBuilder;
    import org.junit.Test;
    
    import com.pjf.mybatis.dao.HotelMapper;
    import com.pjf.mybatis.po.Hotel;
    
    public class TestHotel {
    
        public SqlSessionFactory sqlSessionFactory() throws IOException {
            // mybatis的配置文件
            String resource = "mybatis_config.xml";
            // 使用类加载器加载mybatis的配置文件（它也加载关联的映射文件）TestHotel.class.getClassLoader()
            InputStream is = Resources.getResourceAsStream(resource);
            // 构建sqlSession的工厂
            SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(is);
            return sessionFactory;
        }
        // 查
        @Test
        public void getHotel() throws IOException {
    
            SqlSessionFactory sessionFactory = sqlSessionFactory();
            SqlSession session = sessionFactory.openSession();
            HotelMapper hotelMapper = session.getMapper(HotelMapper.class);
            System.out.println(hotelMapper.getClass());
            //直接返回Hotel对象，打印出来        
            Hotel hotel = hotelMapper.getHotel(1001);
            System.out.println(hotel);
            session.close();
        }

### 2、List类型 ###

返回值为List类型，resultType为List中对象的类型，如List<Hotel>，resultType为Hotel

实例：

hotelMapper接口：

package com.pjf.mybatis.dao;
    
    import java.util.List;
    
    import com.pjf.mybatis.po.Hotel;
    
    public interface HotelMapper {
        // 返回值为List
        public List<Hotel> getHotel(Integer i);

hotelMapper.xml

<?xml version="1.0" encoding="UTF-8" ?>
    <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
    <mapper namespace="com.pjf.mybatis.dao.HotelMapper">
        
        <select id="getHotel" resultType="com.pjf.mybatis.po.Hotel">
            select * from hotel
            where
            price>#{price}
        </select>
    </mapper

测试类

package com.pjf.mybatis;
    
    import java.io.IOException;
    import java.io.InputStream;
    
    import org.apache.ibatis.io.Resources;
    import org.apache.ibatis.session.SqlSession;
    import org.apache.ibatis.session.SqlSessionFactory;
    import org.apache.ibatis.session.SqlSessionFactoryBuilder;
    import org.junit.Test;
    
    import com.pjf.mybatis.dao.HotelMapper;
    import com.pjf.mybatis.po.Hotel;
    
    public class TestHotel {
    
        public SqlSessionFactory sqlSessionFactory() throws IOException {
            // mybatis的配置文件
            String resource = "mybatis_config.xml";
            // 使用类加载器加载mybatis的配置文件（它也加载关联的映射文件）TestHotel.class.getClassLoader()
            InputStream is = Resources.getResourceAsStream(resource);
            // 构建sqlSession的工厂
            SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(is);
            return sessionFactory;
        }
    
        // 查
        @Test
        public void getHotel() throws IOException {
    
            SqlSessionFactory sessionFactory = sqlSessionFactory();
            SqlSession session = sessionFactory.openSession();
            HotelMapper hotelMapper = session.getMapper(HotelMapper.class);
            System.out.println(hotelMapper.getClass());
            // 返回值为List
            List<Hotel> list = hotelMapper.getHotel(1000);
            for (Hotel hotel : list) {
                System.out.println(hotel);
            }
            session.close();
        }

### 3、Map类型 ###

a、返回单条记录的map，key为属性，值为属性值。resultType为map

hotelMapper接口

package com.pjf.mybatis.dao;
    
    import java.util.Map;
    import com.pjf.mybatis.po.Hotel;
    
    public interface HotelMapper {
        // 返回值为Map，key为属性名，value为属性值
        public Map<String, Object> getHotel(Integer i);

hotelMapper.xml

<?xml version="1.0" encoding="UTF-8" ?>
    <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
    <mapper namespace="com.pjf.mybatis.dao.HotelMapper">
        
        <select id="getHotel" resultType="map">
            select * from hotel
            where  id=#{id}
        </select>
    </mapper

测试类，返回id=1001的酒店

package com.pjf.mybatis;
    
    import java.io.IOException;
    import java.io.InputStream;
    import java.util.Map;
    
    import org.apache.ibatis.io.Resources;
    import org.apache.ibatis.session.SqlSession;
    import org.apache.ibatis.session.SqlSessionFactory;
    import org.apache.ibatis.session.SqlSessionFactoryBuilder;
    import org.junit.Test;
    
    import com.pjf.mybatis.dao.HotelMapper;
    import com.pjf.mybatis.po.Hotel;
    
    public class TestHotel {
    
        public SqlSessionFactory sqlSessionFactory() throws IOException {
            // mybatis的配置文件
            String resource = "mybatis_config.xml";
            // 使用类加载器加载mybatis的配置文件（它也加载关联的映射文件）TestHotel.class.getClassLoader()
            InputStream is = Resources.getResourceAsStream(resource);
            // 构建sqlSession的工厂
            SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(is);
            return sessionFactory;
        }
    
        // 查
        @Test
        public void getHotel() throws IOException {
    
            SqlSessionFactory sessionFactory = sqlSessionFactory();
            SqlSession session = sessionFactory.openSession();
            HotelMapper hotelMapper = session.getMapper(HotelMapper.class);
            System.out.println(hotelMapper.getClass());
            // 返回值为map
            Map<String, Object> map = hotelMapper.getHotel(1001);
            System.out.println(map);
            session.close();
        }

b、返回多条记录的map，key为任意一属性，值为对象类型。如Map<String,Hotel>,resultType为Hotel

返回多条记录的map时，key为任意一属性，值为对象类型，不过key需要通过@MapKey("hotelName")指定对象中一个属性名为key

实例：

hotelMapper接口

package com.pjf.mybatis.dao;
    
    import java.util.Map;
    import org.apache.ibatis.annotations.MapKey;
    
    import com.pjf.mybatis.po.Hotel;
    
    public interface HotelMapper {
        // 返回值为Map，key需要通过@MapKey("属性名")来指定javaBean中的一个属性名为key，value为对象
        @MapKey("hotelName")
        public Map<String, Hotel> getHotel(Integer i);

hotelMapper.xml文件

<?xml version="1.0" encoding="UTF-8" ?>
    <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
    <mapper namespace="com.pjf.mybatis.dao.HotelMapper">
        
        <select id="getHotel" resultType="com.pjf.mybatis.po.Hotel">
            select * from hotel
            where
            price>#{price}
        </select>
    </mapper

测试类：返回价格>1000以上的酒店

package com.pjf.mybatis;
    
    import java.io.IOException;
    import java.io.InputStream;
    import java.util.Map;
    
    import org.apache.ibatis.io.Resources;
    import org.apache.ibatis.session.SqlSession;
    import org.apache.ibatis.session.SqlSessionFactory;
    import org.apache.ibatis.session.SqlSessionFactoryBuilder;
    import org.junit.Test;
    
    import com.pjf.mybatis.dao.HotelMapper;
    import com.pjf.mybatis.po.Hotel;
    
    public class TestHotel {
    
        public SqlSessionFactory sqlSessionFactory() throws IOException {
            // mybatis的配置文件
            String resource = "mybatis_config.xml";
            // 使用类加载器加载mybatis的配置文件（它也加载关联的映射文件）TestHotel.class.getClassLoader()
            InputStream is = Resources.getResourceAsStream(resource);
            // 构建sqlSession的工厂
            SqlSessionFactory sessionFactory = new SqlSessionFactoryBuilder().build(is);
            return sessionFactory;
        }
    
        // 查
        @Test
        public void getHotel() throws IOException {
    
            SqlSessionFactory sessionFactory = sqlSessionFactory();
            SqlSession session = sessionFactory.openSession();
            HotelMapper hotelMapper = session.getMapper(HotelMapper.class);
            System.out.println(hotelMapper.getClass());
            // 返回值为map
            Map<String, Hotel> map = hotelMapper.getHotel(1000);
            System.out.println(map);
            session.close();
        }
    }