project is developed based on Spring Boot and Mybatis, and the integrated environment is IDEA.
when I was a beginner, I didn"t understand version management, so I pasted the classes in a runnable project, such as service,controller, and pasted them directly into another project. The past classes or mapper files could not be scanned, but it didn"t necessarily happen. For example, if I deleted the project that went wrong and tried it again, it might be all right.!!?. I feel that this problem is very strange, although it is not very serious, but I don"t know exactly why it happened.