When encountering the error message “a problem was encountered using tagextrainfo class org.apache.taglibs.standard.tei.foreachtei for ‘c:foreach'”, it typically indicates an issue with the “c:foreach” tag in the JSTL library. This error occurs when the necessary tag extra information (tagextrainfo) class is not found or is being used incorrectly.
Here’s an example that demonstrates how to properly use the “c:foreach” tag in JSTL:
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<html>
<head>
<title>Example using c:foreach</title>
</head>
<body>
<c:set var="numbers" value="1,2,3,4,5" />
<ul>
<c:forEach items="${numbers}" var="number">
<li>${number}</li>
</c:forEach>
</ul>
</body>
</html>
In the above example, we first declare the JSTL core taglib using the “taglib” directive. Then, we define a variable called “numbers” using the “c:set” tag and assign it a comma-separated list of numbers. Inside the “c:forEach” tag, we iterate through the “numbers” variable using the “items” attribute. For each iteration, the current value is assigned to the “number” variable, which we can then print within an <li> tag using the expression language (${number}).
Make sure that you have the necessary JSTL libraries properly included in your project’s classpath or web application’s “lib” folder. Also, ensure that the correct version of JSTL library is being used.