Regular expression to remove special characters in JSTL tags

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The JSTL fn:replace() does not use a regular expression based replacement. It’s just an exact charsequence-by-charsequence replacement, exactly like as String#replace() does.

JSTL does not offer another EL function for that. You could just homegrow an EL function yourself which delegates to the regex based String#replaceAll().

E.g.

package com.example;

public final class Functions {

     private Functions() {
         //
     }

     public static String replaceAll(String string, String pattern, String replacement) {
         return string.replaceAll(pattern, replacement);
     }

}

Which you register in a /WEB-INF/functions.tld file as follows:

<?xml version="1.0" encoding="UTF-8" ?>
<taglib 
    xmlns="http://java.sun.com/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-jsptaglibrary_2_1.xsd"
    version="2.1">

    <display-name>Custom Functions</display-name>    
    <tlib-version>1.0</tlib-version>
    <uri>http://example.com/functions</uri>

    <function>
        <name>replaceAll</name>
        <function-class>com.example.Functions</function-class>
        <function-signature>java.lang.String replaceAll(java.lang.String, java.lang.String, java.lang.String)</function-signature>
    </function>
</taglib>

And finally use as below:

<%@taglib uri="http://example.com/functions" prefix="f" %>

...

${f:replaceAll(repOption, '[^A-Za-z]', '')}

Or, if you’re already on Servlet 3.0 / EL 2.2 or newer (Tomcat 7 or newer), wherein EL started to support invoking methods with arguments, simply directly invoke String#replaceAll() method on the string instance.

${repOption.replaceAll('[^A-Za-z]', '')}

See also:

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