There is a project developed in Struts 1 to be migrated to Struts 2.
The application has a lot of custom tags were written using Struts 1. So when migrating to Struts 2 is there a way that I can keep those custom tag support for existing JSPs.
But we suppose to remove all the Struts 1.x related jars when migrating to Struts 2, so rewriting those custom tags with Struts 2 is a huge effort.
If they are using Struts1 and you remove it, then you should remove tags dependent on it. However, you can use any other taglibs, including JSTL corresponding to your JSP specification version.