well you need to understand there are always two things the API and the implementation (mind the gradle format of the following code)
compile group:'javax.servlet.jsp.jstl', name:'javax.servlet.jsp.jstl-api', version:'1.2.1'
compile group:'org.glassfish.web', name:'javax.servlet.jsp.jstl',version:'1.2.1'
so If you're using a servlet container with no jstl support then of course it will not provide both of them, a mistake which I made is that I only put the first one, but if you're using full stack application server i.e glassfish then glassfish will have both of them already inside.