Packaging tag files directly in a web application , The JSP container must generate an implicit tag library for each directory
under and including /WEB-INF/tags/. This tag library can be imported only via the
tagdir attribute of the taglib directive.
But If you placed your tag files as a JAR under META-INF/tags directory then have to declared a explicit tag library OR TLD file to mention the location of that tag files.
<tag-file>
<name>
<path>
<tag-file> element should be used in that case.
Please refer JSP specification 2.0 (JSP.8.4.3 Packaging Directly in a Web Application)
I hope this will help
Thanks
Poonam