The "JSP el" El expression gets the list length/no loop, and EL takes the contents of the first item directly in the list/el gets the map key, the value of the map

1.EL expression Get list length

<%@ taglib uri= "Http://java.sun.com/jsp/jstl/core" prefix= "C"%>
<%@ taglib prefix= "FN" uri= "Http://java.sun.com/jsp/jstl/functions"%>

<c:if test= "${fn:length (list name) >1}" >

What do you do in the middle?

</c:if>

2. No loop, El gets the contents of the first item directly in the list

${list[0]. Properties}

3.EL gets the key of the map, the value of the map

<c:foreach items= "${map name}" var= "K" >
<option value= "${k.key}" >${k.value}</option>
</c:forEach>

This gets the keys and values separately.

The "JSP el" El expression gets the list length/no loop, and EL takes the contents of the first item directly in the list/el gets the map key, the value of the map