准备

MyBatis内部可以帮我们生成dao接口的实现类（代理类，dao接口的代理）

使用这种代理机制的前提是，SqlMapper.xml文件中的namespace必须是dao接口的全限定名称，id必须是dao接口的方法名

开始

创建一个SpringBoot项目，这里我们采用SqlSeeion开发

目录结构如下

1. controller/CarController

@RestController
public class CarController {

    @PostMapping("/insert")
    public String insert(@RequestBody Car car){
        SqlSession sqlSession= SqlSessionUtil.createSqlSession();
        CarMapper carMapper=sqlSession.getMapper(CarMapper.class);
        carMapper.insert(car);

        sqlSession.commit();
        return "success";
    }

    @PostMapping("/delete")
    public String delete(Long id){
        SqlSession sqlSession= SqlSessionUtil.createSqlSession();
        CarMapper carMapper=sqlSession.getMapper(CarMapper.class);
        carMapper.delete(id);

        sqlSession.commit();
        return "success";
    }

    @PostMapping("/update")
    public String update(@RequestBody Car car){
        SqlSession sqlSession= SqlSessionUtil.createSqlSession();
        CarMapper carMapper=sqlSession.getMapper(CarMapper.class);
        carMapper.update(car);

        sqlSession.commit();
        return "success";
    }

    @PostMapping("/select")
    public Car selectById(Long id){
        SqlSession sqlSession= SqlSessionUtil.createSqlSession();
        CarMapper carMapper=sqlSession.getMapper(CarMapper.class);
        return carMapper.selectById(id);
    }
    
    @PostMapping("/selectAll")
    public List<Car> selectAll(){
        SqlSession sqlSession= SqlSessionUtil.createSqlSession();
        CarMapper carMapper=sqlSession.getMapper(CarMapper.class);
        return carMapper.selectAll();
    }
}

2. mapper/CarMapper

public interface CarMapper {

    Integer insert(Car car);

    Integer update(Car car);

    Integer delete(Long id );

    Car selectById(Long id);

    List<Car> selectAll();
}

3. pojo/Car

@Data
@AllArgsConstructor
@NoArgsConstructor
public class Car {

  private Long id;
  private String carNum;
  private String brand;
  private Double guidePrice;
  private String produceTime;
  private String carType;

}

4. utils/SqlSessionUtil

public class SqlSessionUtil {

    private SqlSessionUtil() {}

    private static SqlSessionFactory sqlSessionFactory;

    static {
        try {
            SqlSessionFactoryBuilder sqlSessionFactoryBuilder = new SqlSessionFactoryBuilder();
            sqlSessionFactory = sqlSessionFactoryBuilder.build(Resources.getResourceAsStream("ApplicationContext.xml"),"development");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static SqlSession createSqlSession() {
        return sqlSessionFactory.openSession();
    }

}

5. CarMapper.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.example.webapplication.Mapper.CarMapper">
    <insert id="insert">
        insert into  car( car_num, brand, guide_price, produce_time, car_type)
        values (#{carNum},#{brand},#{guidePrice},#{produceTime},#{carType})
    </insert>
    <update id="update">
        update car set
        car_num=#{carNum},
        brand=#{brand},
        guide_price=#{guidePrice},
        produce_time=#{produceTime},
        car_type=#{carType}
        where id=#{id}
    </update>
    <delete id="delete">
        delete  from car where id=#{id}
    </delete>
    <select id="selectById" resultType="com.example.webapplication.pojo.Car">
        select
            id,
            car_num as  carNum,
            brand,
            guide_price as guidePrice,
            produce_time as produceTime,
            car_type as carType
            from car where id=#{id}
    </select>
    <select id="selectAll" resultType="com.example.webapplication.pojo.Car">
        select
            id,
            car_num as  carNum,
            brand,
            guide_price as guidePrice,
            produce_time as produceTime,
            car_type as carType
            from car
    </select>
</mapper>

6. ApplicationContext.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.cj.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306/test"/>
                <property name="username" value="root"/>
                <property name="password" value="asd60787533"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="com/example/webapplication/Mapper/CarMapper.xml"/>
    </mappers>
</configuration>