mybatis配置及使用步骤

• • 1.类型别名
  • 2.结果集映射ResultMap
  • 3.mybatis使用步骤

注意：接口和它的Mapper配置文件最好同名，在同一包下

UserMapper.xml就可以直接用User了

     select * from mybatis_study.user where id= #{id};

主要用于解决属性名与数据库表中字段不一致

实体类属性

表字段

运行结果

解决方法：

resultMap结果集映射

UserMapper.xml
.

1.导入mysql驱动和mybatis、lombok依赖

    
        mysql
        mysql-connector-java
        8.0.27
    
    
        org.mybatis
        mybatis
        3.5.7
    
    
        org.projectlombok
        lombok
        1.18.20
        provided
    

2.编写mybatis-config.xml配置文件

3.db.properties文件

driver=com.mysql.cj.jdbc.Driver
url=jdbc:mysql://localhost:3306/mybatis_study?serverTimezome=UTC
username=root
password=123456

4.工具类utils下的MybatisUtil.Java

public class MybatisUtil {
    private static SqlSessionFactory factory;
    static{
        try {
            //1.读取配置文件
            InputStream inputStream = Resources.getResourceAsStream("mybatis-config.xml");
            //2.创建SqlsessionFactory工厂
            factory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    public static SqlSession getSqlSession(){
      //3.使用工厂生产sqlsession对象
      return factory.openSession();
    }
}

5.pojo实体类User.java

@Data
public class User{
    private Integer id;
    private String name;
    private String sex;
    private String address;
}

6.对应Mapper接口

public interface UserMapper {
    //查询全部用户
    List findAll();
    //根据ID查找
    User getUserId(int id);
    //添加用户
    int addUser(User user);
    //更新用户
    int updateUser(User user);
    //删除用户
    int deleteUser(int id);
}

7.对应的Mapper.xml文件

    
    
    
        select * from user;
    
    
    
        select * from mybatis_study.user where id= #{id};
    
    
    
        insert into user (id,username,sex,address) values (#{id},#{username},#{sex},#{address});
    
    
    
        update user set username=#{username},sex=#{sex},address=#{address} where id = #{id};
    
    
    
        delete from user where id = #{id}
    

8.测试类

//查询所有
    @Test
    public void TestList(){
        SqlSession session = MybatisUtil.getSqlSession();
        UserMapper userMapper = session.getMapper(UserMapper.class);
        List list = userMapper.findAll();
        for (User user : list) {
            System.out.println(user);
        }
        //释放资源
        session.close();
    }
    //根据ID查询
    @Test
    public void getUserId(){
        SqlSession session = MybatisUtil.getSqlSession();
        UserMapper mapper = session.getMapper(UserMapper.class);
        User userId = mapper.getUserId(41);
        System.out.println(userId);
        session.close();
    }
    //添加操作,增删改都需要提交事务
    @Test
    public void addUser(){
        SqlSession session = MybatisUtil.getSqlSession();
        UserMapper mapper = session.getMapper(UserMapper.class);
        mapper.addUser(new User(3, "小哈", "男", "新乡市"));
        //提交事务
        session.commit();
        session.close();
    }
    //更新操作
    @Test
    public void updateUser(){
        SqlSession session = MybatisUtil.getSqlSession();
        UserMapper mapper = session.getMapper(UserMapper.class);
        mapper.updateUser(new User(3,"小何","女","河南省"));
        //提交事务
        session.commit();
        session.close();
    }
    //删除操作
    @Test
    public void deleteUser(){
        SqlSession session = MybatisUtil.getSqlSession();
        UserMapper mapper = session.getMapper(UserMapper.class);
        mapper.deleteUser(3);
        session.commit();
        session.close();
    }