EL Tags:
JSTL: JSP Standard Tag Library
Core tag library:
Usage: 1, introduced into the jar package 2, the introduction page: <% @ taglib uri = " http://java.sun.com/jsp/jstl/core" prefix = "c"%>
Tags Categories:
Expression operation: out, set, remove, catch // (this almost no)
Process control: if, choose (when, otherwise)
Iterations: forEach, forTokens
URL操作：Import， param， url, redirect, forward