mybatis學習（七）——resultType解析

resultType是sql映射文件中定義返回值類型，返回值有基本類型，對象類型，List類型，Map類型等。現總結一下再解釋

總結：

resultType:

1、基本類型  ：resultType=基本類型

2、List類型：   resultType=List中元素的類型

3、Map類型    單條記錄：resultType =map

                          多條記錄：resultType =Map中value的類型

1、對象類型

對於對象類型resultType直接寫對象的全類名就可以了

實例：

hotelMapper接口

package com.pjf.mybatis.dao;

import com.pjf.mybatis.po.Hotel;

public interface HotelMapper {
    //返回值類型為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直接寫對象的全類名 -->
    <select id="getHotel" resultType="com.pjf.mybatis.po.Hotel">
        select * from hotel
        where
        id=#{id}
    </select>
</mapper>

測試類：

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";
        // 使用類加載器加載mybatis的配置文件（它也加載關聯的映射文件）TestHotel.class.getClassLoader()
        InputStream is = Resources.getResourceAsStream(resource);
        // 構建sqlSession的工廠
        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對象，打印出來        
        Hotel hotel = hotelMapper.getHotel(1001);
        System.out.println(hotel);
        session.close();
    }

}

2、List類型

返回值為List類型，resultType為List中對象的類型，如List<Hotel>，resultType為Hotel

實例：

hotelMapper接口

package com.pjf.mybatis.dao;

import java.util.List;

import com.pjf.mybatis.po.Hotel;

public interface HotelMapper {
    // 返回值為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">
    <!-- 返回值為List，resultType為List中元素的全類名 -->
    <select id="getHotel" resultType="com.pjf.mybatis.po.Hotel">
        select * from hotel
        where
        price>#{price}
    </select>
</mapper>

測試類

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";
        // 使用類加載器加載mybatis的配置文件（它也加載關聯的映射文件）TestHotel.class.getClassLoader()
        InputStream is = Resources.getResourceAsStream(resource);
        // 構建sqlSession的工廠
        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());
        // 返回值為List
        List<Hotel> list = hotelMapper.getHotel(1000);
        for (Hotel hotel : list) {
            System.out.println(hotel);
        }
        session.close();
    }
}

3、Map類型

a、返回單條記錄的map，key為屬性，值為屬性值。resultType為map

hotelMapper接口

package com.pjf.mybatis.dao;

import java.util.Map;
import com.pjf.mybatis.po.Hotel;

public interface HotelMapper {
    // 返回值為Map，key為屬性名，value為屬性值
    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">
    <!-- 返回值為map，resultType為map -->
    <select id="getHotel" resultType="map">
        select * from hotel
        where
        id=#{id}
    </select>
</mapper>

測試類，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";
        // 使用類加載器加載mybatis的配置文件（它也加載關聯的映射文件）TestHotel.class.getClassLoader()
        InputStream is = Resources.getResourceAsStream(resource);
        // 構建sqlSession的工廠
        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());
        // 返回值為map
        Map<String, Object> map = hotelMapper.getHotel(1001);
        System.out.println(map);
        session.close();
    }
}

b、返回多條記錄的map，key為任意一屬性，值為對象類型。如Map<String,Hotel>,resultType為Hotel

返回多條記錄的map時，key為任意一屬性，值為對象類型，不過key需要通過@MapKey("hotelName")指定對象中一個屬性名為key

實例：

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 {
    // 返回值為Map，key需要通過@MapKey("屬性名")來指定javaBean中的一個屬性名為key，value為對象
    @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">
    <!-- 返回值為map，resultType為對象的全類名 -->
    <select id="getHotel" resultType="com.pjf.mybatis.po.Hotel">
        select * from hotel
        where
        price>#{price}
    </select>
</mapper>

測試類：返回價格>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";
        // 使用類加載器加載mybatis的配置文件（它也加載關聯的映射文件）TestHotel.class.getClassLoader()
        InputStream is = Resources.getResourceAsStream(resource);
        // 構建sqlSession的工廠
        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());
        // 返回值為map
        Map<String, Hotel> map = hotelMapper.getHotel(1000);
        System.out.println(map);
        session.close();
    }
}