You'd better send your error message, so it's clear at a glance. Look at your code:

: If a nullpointer appears when displaying the information of booksearchinfo, it must be a session. Set properties ("borrowed information", borrowed information);

That is, borrowedinfos is null, which may be listborrowedinfo = dao.getborrowedbookinfo (userid); Get null value

2. If it appears in the BorrowedBookController, it is probably borrowedbookdaodao = daomanager.getdao (borrowedbookdao.class); Dao is empty.

I hope I can help you.