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(); } }