Question about El expression output in JSP

When we used the El expression yesterday, the El expression could not get the value in the Variable. After checking the information, we can see that it is related to the servlet/jsp version, el expressions can be used only in servlet 2.4/jsp 2.0. In other versions, you must add <% @ page iselignored = "false" %> at the beginning of JSP. View the JSP version. In the Web. xml file

<Web-app version = "2.4"
Xmlns = "http://java.sun.com/xml/ns/j2ee"
Xmlns: xsi = "http://www.w3.org/2001/XMLSchema-instance"
Xsi: schemalocation = "http://java.sun.com/xml/ns/j2ee
Http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd>

Servlet 2.4/jsp 2.0

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