@Autowired
private BrandMapper brandMapper;

以上代码brandMapper经常爆红，程序却能正常运行，经度娘搜索后得出完美解决方案。网址链接：https://blog.csdn.net/Coder_Knight/article/details/83999139
Mapper文件中添加@Repository注解。

例如

@Repository
public interface BrandMapper extends Mapper<Brand> {

}

Idea解决Mapper注入爆红问题