@SpringBootApplication cannot be resolved to a type In STS
学习了：https://stackoverflow.com/questions/41668819/springbootapplication-cannot-be-resolved-to-a-type-in-sts
找到maven仓库目录 C:UsersYourUser.m2
epositoryorgspringframeworkoot ，
然后删除：spring-boot-autoconfigure 文件夹；
然后回到eclipse中进行maven - update project
This solved the problem for me too.