一：MyBatis的注解式开发

官⽅是这么说的：

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！使用注解式开发以后三兄弟之一的SqlMapper.xml文件就不需要了！

1. @Insert注解

二兄弟之一CarMapper接口，用来编写方法

package com.bjpowernode.mybatis.mapper;

import com.bjpowernode.mybatis.pojo.Car;
import org.apache.ibatis.annotations.Insert;

public interface CarMapper {
    // 使用注解式开发，插入数据
    @Insert("insert into t_car values(null,#{carNum},#{brand},#{guidePrice},#{produceTime},#{carType})")
    int insert(Car car);
}

二兄弟之二CarMapperTest，用来测试

package com.bjpowernode.mybatis.test;

import com.bjpowernode.mybatis.mapper.CarMapper;
import com.bjpowernode.mybatis.pojo.Car;
import com.bjpowernode.mybatis.utils.SqlSessionUtil;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

public class CarMapperTest {
    @Test
    public void testInsert(){
        SqlSession sqlSession = SqlSessionUtil.openSession();
        CarMapper mapper = sqlSession.getMapper(CarMapper.class);
        // 创建Car对象
        Car car = new Car(null, "666", "丰田霸道", 32.0, "2023-1-9", "燃油车");
        int count = mapper.insert(car);
        System.out.println(count);
        sqlSession.commit();
        sqlSession.close();
    }
}

执行结果：

2. @Delete注解

二兄弟之一CarMapper接口，用来编写方法

package com.bjpowernode.mybatis.mapper;

import com.bjpowernode.mybatis.pojo.Car;
import org.apache.ibatis.annotations.Insert;

public interface CarMapper {
    // 使用注解式开发，删除数据
    @Delete("delete from t_car where id = #{id}")
    int deleteById(Long id);
}

二兄弟之二CarMapperTest，用来测试

package com.bjpowernode.mybatis.test;

import com.bjpowernode.mybatis.mapper.CarMapper;
import com.bjpowernode.mybatis.pojo.Car;
import com.bjpowernode.mybatis.utils.SqlSessionUtil;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

public class CarMapperTest {
   @Test
    public void testDeleteById(){
        SqlSession sqlSession = SqlSessionUtil.openSession();
        CarMapper mapper = sqlSession.getMapper(CarMapper.class);
        int count = mapper.deleteById(40L);
        System.out.println(count);
        sqlSession.commit();
        sqlSession.close();
    }
}

执行结果：

3. @Update注解

二兄弟之一CarMapper接口，用来编写方法

package com.bjpowernode.mybatis.mapper;

import com.bjpowernode.mybatis.pojo.Car;
import org.apache.ibatis.annotations.Insert;

public interface CarMapper {
    // 使用注解式开发，更新数据
    @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);
}

二兄弟之二CarMapperTest，用来测试

package com.bjpowernode.mybatis.test;

import com.bjpowernode.mybatis.mapper.CarMapper;
import com.bjpowernode.mybatis.pojo.Car;
import com.bjpowernode.mybatis.utils.SqlSessionUtil;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

public class CarMapperTest {
   @Test
    public void testUpdate(){
        SqlSession sqlSession = SqlSessionUtil.openSession();
        CarMapper mapper = sqlSession.getMapper(CarMapper.class);
        // 创建Car对象，根据id进行更新
        Car car = new Car(34L, "666", "丰田霸道", 32.0, "2023-1-9", "燃油车");
        int count = mapper.update(car);
        System.out.println(count);
        sqlSession.commit();
        sqlSession.close();
    }
}

执行结果：

4. @Select注解

二兄弟之一CarMapper接口，用来编写方法

package com.bjpowernode.mybatis.mapper;

import com.bjpowernode.mybatis.pojo.Car;
import org.apache.ibatis.annotations.Insert;

public interface CarMapper {
    // 使用注解式开发，查询数据
    @Select("select * from t_car where id = #{id}")
    Car selectById(Long id);
}

二兄弟之二CarMapperTest，用来测试

package com.bjpowernode.mybatis.test;

import com.bjpowernode.mybatis.mapper.CarMapper;
import com.bjpowernode.mybatis.pojo.Car;
import com.bjpowernode.mybatis.utils.SqlSessionUtil;
import org.apache.ibatis.session.SqlSession;
import org.junit.Test;

public class CarMapperTest {
   @Test
    public void testSelectById(){
        SqlSession sqlSession = SqlSessionUtil.openSession();
        CarMapper mapper = sqlSession.getMapper(CarMapper.class);
        Car car = mapper.selectById(41L);
        System.out.println(car);
        sqlSession.close();
    }
}

执行结果：

5. @Results注解

    <!--启⽤驼峰命名⾃动映射-->
    <settings>
        <setting name="mapUnderscoreToCamelCase" value="true"/>
    </settings>

package com.bjpowernode.mybatis.mapper;

import com.bjpowernode.mybatis.pojo.Car;
import org.apache.ibatis.annotations.*;

public interface CarMapper {
    // 使用注解式开发，查询数据
    @Select("select * from t_car where id = #{id}")
    @Results({
            @Result(property = "id",column = "id"),
            @Result(property = "carNum",column = "car_num"),
            @Result(property = "brand",column = "brand"),
            @Result(property = "guidePrice",column = "guide_price"),
            @Result(property = "produceTime",column = "produce_time"),
            @Result(property = "carType",column = "car_type"),
    })
    Car selectById(Long id);
}