Cause analysis: there is an error in the jar package. You need to re import the jar package
first click the jeesite project, and then open properties → Java build path → libraries

Then remove all jar packages that report errors, click apply and close, select all jar packages in the Lib directory, and right-click build path to re import jar packages

errors are still reported for individual files after re introduction, as follows

The reason is that some packages are not included after Java se 9.0. If they are used, they need to be imported manually
a link is given below. You can go to this website to download the required packages by yourself
http://www.java2s.com/Code/Jar/CatalogJar.htm