mybatis Mapper 中resultType使用方法及返回值为Map的写法 mybatis学习（七）——resultType解析

 

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：

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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(); } }