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

select * from hotel

where

id=#{id}

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，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 getHotel(Integer i);

}

hotelMapper.xml

select * from hotel

where

price>#{price}

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 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 getHotel(Integer i);

}

hotelMapper.xml

select * from hotel

where

id=#{id}

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 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,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 getHotel(Integer i);

}

hotelMapper.xml文件

select * from hotel

where

price>#{price}

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 map = hotelMapper.getHotel(1000);

System.out.println(map);

session.close();

}

}