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:
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(); } }