Mybatis(3增删改查)

MyBatis 的真正强大在于它的语句映射&＃xff0c;这是它的魔力所在。

创建接口

public interface UserInfoMapper {/*** 查找&＃xff1a;* 查找所有用户* 根据id查找单个用户* &＃64;return*/List selectAllUsers();UserInfo selectUserById(Long userId);//新增一条数据Integer insetUserInfo(UserInfo userInfo);//根据id删除用户Integer deleteUserInfo(Long userId);//根据id修改用户名字Integer updateUserInfo( &＃64;Param("id") Long userId,&＃64;Param("name") String userName);
}

接口创建完毕后更改mapper中的命名空间

配置映射

id与接口名需对应


select * from user_infoselect * from user_info where user_id&＃61;#{id}insert into user_info(username,user_password,create_time,update_time) values(#{userName},#{userPassword},now(),now())delete from user_info where user_id&＃61;#{id}update user_info set username&＃61;#{name},update_time&＃61;now() where user_id&＃61;#{id}


注意传入多个参数情况&＃xff0c;在接口处使用&＃64;Param(*)让其与#{*}对应

查

对sqlSession进行封装使得代码简洁

private static SqlSession getSqlSession() throws IOException {String resource &＃61; "mybatis-config.xml";InputStream inputStream &＃61; Resources.getResourceAsStream(resource);SqlSessionFactory sqlSessionFactory &＃61; new SqlSessionFactoryBuilder().build(inputStream);return sqlSessionFactory.openSession();}

查找全部用户

public static void main( String[] args ) throws Exception{SqlSession sqlSession &＃61; getSqlSession();UserInfoMapper mapper&＃61;sqlSession.getMapper(UserInfoMapper.class);List userInfos&＃61;mapper.selectAllUsers();for (UserInfo userInfo : userInfos) {System.out.println(userInfo);}sqlSession.close();}

根据id查找某个用户

public static void main( String[] args ) throws Exception{SqlSession sqlSession &＃61; getSqlSession();UserInfoMapper mapper&＃61;sqlSession.getMapper(UserInfoMapper.class);UserInfo userInfo&＃61;mapper.selectUserById(1L);System.out.println(userInfo);sqlSession.close();}

增

public static void main( String[] args ) throws Exception{SqlSession sqlSession &＃61; getSqlSession();UserInfoMapper mapper&＃61;sqlSession.getMapper(UserInfoMapper.class);UserInfo userInfo&＃61;new UserInfo();userInfo.setUserName("wangwu");userInfo.setUserPassword("12345");mapper.insetUserInfo(userInfo);sqlSession.commit();sqlSession.close();}

删

public static void main( String[] args ) throws Exception{SqlSession sqlSession &＃61; getSqlSession();UserInfoMapper mapper&＃61;sqlSession.getMapper(UserInfoMapper.class);mapper.deleteUserInfo(3L);sqlSession.commit();sqlSession.close();}

改

public static void main( String[] args ) throws Exception{SqlSession sqlSession &＃61; getSqlSession();UserInfoMapper mapper&＃61;sqlSession.getMapper(UserInfoMapper.class);mapper.updateUserInfo(2L,"wangwu");sqlSession.commit();sqlSession.close();}

使用和指定语句的参数和返回值相匹配的接口&＃xff08;比如 BlogMapper.class&＃xff09;&＃xff0c;现在你的代码不仅更清晰&＃xff0c;更加类型安全&＃xff0c;还不用担心可能出错的字符串字面值以及强制类型转换。