十七 MyBatis的注解式开发

十七、MyBatis的注解式开发

mybatis中也提供了注解式开发方式，采用注解可以减少Sql映射文件的配置。
当然，使用注解式开发的话，sql语句是写在java程序中的，这种方式也会给sql语句的维护带来成本。
官方是这么说的：

使用注解来映射简单语句会使代码显得更加简洁，但对于稍微复杂一点的语句，Java 注解不仅力不从心，还会让你本就复杂的 SQL 语句更加混乱不堪。因此，如果你需要做一些很复杂的操作，最好用 XML 来映射语句。

使用注解编写复杂的SQL是这样的：

原则：简单sql可以注解。复杂sql使用xml。

模块名：mybatis-013-annotation

打包方式：jar

依赖：mybatis，mysql驱动，junit，logback

配置文件：jdbc.properties、mybatis-config.xml、logback.xml

pojo：com.study.mybatis.pojo.Car

mapper接口：com.study.mybatis.mapper.CarMapper

17.1 @Insert

package com.study.mybatis.mapper;import com.study.mybatis.pojo.Car;
import org.apache.ibatis.annotations.Insert;public interface CarMapper {@Insert(value="insert into t_car values(null,#{carNum},#{brand},#{guidePrice},#{produceTime},#{carType})")int insert(Car car);
}

package com.study.mybatis.test;import com.study.mybatis.mapper.CarMapper;
import com.study.mybatis.pojo.Car;
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;public class AnnotationTest {@Testpublic void testInsert() throws Exception{SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(Resources.getResourceAsStream("mybatis-config.xml"));SqlSession sqlSession = sqlSessionFactory.openSession();CarMapper mapper = sqlSession.getMapper(CarMapper.class);Car car = new Car(null, "1112", "卡罗拉", 30.0, "2000-10-10", "燃油车");int count = mapper.insert(car);System.out.println("插入了几条记录：" + count);sqlSession.commit();sqlSession.close();}
}

17.2 @Delete

@Delete("delete from t_car where id = #{id}")
int deleteById(Long id);

@Test
public void testDelete() throws Exception{SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(Resources.getResourceAsStream("mybatis-config.xml"));SqlSession sqlSession = sqlSessionFactory.openSession();CarMapper mapper = sqlSession.getMapper(CarMapper.class);mapper.deleteById(89L);sqlSession.commit();sqlSession.close();
}

17.3 @Update

@Update("update t_car set car_num=#{carNum},brand=#{brand},guide_price=#{guidePrice},produce_time=#{produceTime},car_type=#{carType} where id=#{id}")
int update(Car car);

@Test
public void testUpdate() throws Exception{SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(Resources.getResourceAsStream("mybatis-config.xml"));SqlSession sqlSession = sqlSessionFactory.openSession();CarMapper mapper = sqlSession.getMapper(CarMapper.class);Car car = new Car(88L,"1001", "凯美瑞", 30.0,"2000-11-11", "新能源");mapper.update(car);sqlSession.commit();sqlSession.close();
}

17.4 @Select

@Select("select * from t_car where id = #{id}")
@Results({@Result(column = "id", property = "id", id = true),@Result(column = "car_num", property = "carNum"),@Result(column = "brand", property = "brand"),@Result(column = "guide_price", property = "guidePrice"),@Result(column = "produce_time", property = "produceTime"),@Result(column = "car_type", property = "carType")
})
Car selectById(Long id);

@Test
public void testSelectById() throws Exception{SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(Resources.getResourceAsStream("mybatis-config.xml"));SqlSession sqlSession = sqlSessionFactory.openSession();CarMapper carMapper = sqlSession.getMapper(CarMapper.class);Car car = carMapper.selectById(88L);System.out.println(car);
}