mybatis学习（七）——resultType解析

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">

    <!--resultType直接写对象的全类名 -->

    <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">

    <!-- 返回值为List，resultType为List中元素的全类名 -->

    <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">

    <!-- 返回值为map，resultType为map -->

    <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">

    <!-- 返回值为map，resultType为对象的全类名 -->

    <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();

    }

}