mybatis Mapper 中resultType使用方法及返回值爲Map的寫法

 

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:

一、基本類型  ：resultType=基本類型

二、List類型：   resultType=List中元素的類型

三、Map類型    單條記錄：resultType =map

                          多條記錄：resultType =Map中value的類型

一、對象類型

對於對象類型resultType直接寫對象的全類名就能夠了

實例：

hotelMapper接口

package com.pjf.mybatis.dao; import com.pjf.mybatis.po.Hotel; public interface HotelMapper { //返回值類型爲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(); } }

二、List類型

返回值爲List類型，resultType爲List中對象的類型，如List<Hotel>，resultType爲Hotel

實例：

hotelMapper接口

package com.pjf.mybatis.dao; import java.util.List; import com.pjf.mybatis.po.Hotel; public interface HotelMapper { // 返回值爲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"> <!-- 返回值爲List，resultType爲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()); // 返回值爲List List<Hotel> list = hotelMapper.getHotel(1000); for (Hotel hotel : list) { System.out.println(hotel); } session.close(); } }

三、Map類型

a、返回單條記錄的map，key爲屬性，值爲屬性值。resultType爲map

hotelMapper接口

package com.pjf.mybatis.dao; import java.util.Map; import com.pjf.mybatis.po.Hotel; public interface HotelMapper { // 返回值爲Map，key爲屬性名，value爲屬性值 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"> <!-- 返回值爲map，resultType爲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()); // 返回值爲map Map<String, Object> map = hotelMapper.getHotel(1001); System.out.println(map); session.close(); } }

b、返回多條記錄的map，key爲任意一屬性，值爲對象類型。如Map<String,Hotel>,resultType爲Hotel

返回多條記錄的map時，key爲任意一屬性，值爲對象類型，不過key須要經過@MapKey("hotelName")指定對象中一個屬性名爲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 { // 返回值爲Map，key須要經過@MapKey("屬性名")來指定javaBean中的一個屬性名爲key，value爲對象 @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"> <!-- 返回值爲map，resultType爲對象的全類名 --> <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()); // 返回值爲map Map<String, Hotel> map = hotelMapper.getHotel(1000); System.out.println(map); session.close(); } }