What groups of tags does the JSTL library consist of?

The JSTL (JavaServer Pages Standard Tag Library) library consists of five main groups of tags, each designed for specific tasks in JSP pages.

1. Core (Prefix c): Tags for common tasks such as conditional execution, loops, URL management, and exception handling.

   • c:if
   • c:forEach
   • c:url
   • c:catch

2. Formatting (Prefix fmt): Tags for formatting data such as numbers, dates, currency, and for working with localized messages.

   • fmt:formatNumber
   • fmt:formatDate
   • fmt:message
   • fmt:setLocale

3. SQL (Prefix sql): Tags for interacting with databases without using Java code in JSP.

   • sql:query
   • sql:update
   • sql:param
   • sql:setDataSource

4. XML (Prefix x): Tags for processing XML data.

   • x:parse
   • x:out
   • x:forEach
   • x:if

5. Functions (Prefix fn): A set of standard functions for working with strings and collections. Used in EL (Expression Language).

   • fn:length()
   • fn:startsWith()
   • fn:endsWith()
   • fn:substring()

Example of using a tag from the Core group:

<%-- Declaring the tag library --%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>

<%-- Example of using the c:forEach tag --%>
<c:forEach var="item" items="${myCollection}">
    <p>${item}</p>
</c:forEach>