cannot resolve symbol servlet
Analysis: The reason for this problem is the lack of the corresponding package, as long as the package is imported correctly.
When we use idea, we often put multiple projects on one page. In fact, the essence of this is: the first one is the engineering project, and the other subsequent projects are modules. Once we move the project, we re-import each module Later, due to the separation of the first project, each library is not imported. We need to re-import the library.
Steps: File --> Project Structure --> Modules --> Select the corresponding project --> Dependencies --> Right Click the plus sign on the side, select Libraries --> tick the required library, here is the place you own --> Apply to add it.
