JSP/Servlet | JSTL(JSP Standard Tag Library) | Basic Functions

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JSTL provides several basic functions for development convenience. This section explains those basic functions.

Directive declaration

To use the basic functions, declare the following directive at the top of the JSP page.

<%@ taglib prefix="fn" uri="http://java.sun.com/jsp/jstl/functions"%>

Functions

Function	Return value	Usage	Description
contains	boolean	fn:contains(A, B)	Checks whether string A contains string B.
containsIgnoreCase	boolean	fn:containsIgnoreCase(A, B)	Checks whether A contains B without case sensitivity.
endWith	boolean	fn:endWith(A, B)	Checks whether string A ends with B.
escapeXml	String	fn:escapeXml(A)	If A contains strings defined in XML or HTML, converts them to entity codes.
indexOf	int	fn:indexOf(A, B)	Returns the first index where B appears in string A.
join	String	fn:join(A[], B)	Converts string array A into one string using B as the delimiter.
length	int	fn:length(A)	Returns the total length of a Collection object such as List or ArrayList.
replace	String	fn:replace(A, B, C)	Finds characters matching B in string A and replaces them with C.
split	String[]	fn:split(A, B)	Splits A by the string specified by B and returns an array.
startsWith	String	fn:startsWith(A, B)	Checks whether string A starts with B.
substring	String	fn:substring(A, B, C)	Returns the substring of A from index B to C.
substringAfter	String	fn:substringAfter(A, B)	Returns the substring after B appears in A.
substringBefore	String	fn:substringBefore(A, B)	Returns the substring before B appears in A.
toLowerCase	String	fn:toLowerCase(A)	Converts all of A to lowercase.
toUpperCase	String	fn:toUpperCase(A)	Converts all of A to uppercase.
trim	String	fn:trim(A)	Removes leading and trailing whitespace from string A.

Usage example

toLowerCase, toUpperCase

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%@ taglib prefix="fn" uri="http://java.sun.com/jsp/jstl/functions" %>
<html>
   <head>
      <title>JSTL Functions</title>
   </head>
   <body>
      <c:set var="str" value="My name is DevKama"/>
      <p>Lower Case : ${fn:toLowerCase(str)}</p>
      <p>Upper Case : ${fn:toUpperCase(str)}</p>
   </body>
</html>

Output result

my name is devkama
MY NAME IS DEVKUMA