How can I parse a url using JSP / JSTL?

This feature does not exist in JSTL. The closest is fn:replace()

, but it doesn't support regular expressions. Other functions provide the ability to get rid of the leading part before the domain (using fn:substringAfter()

a multiple times on //

and /

), but there is nothing that makes it easier to get rid of the back part. Maybe with a whole series fn:substringAfter

and c:set

in a loop, but this will make the code clunky and won't really be reused.

Well, in regex, you can use ^[^/]+/+[^/]+|[^/]+$

for this:

url = url.replaceAll("^[^/]+/+[^/]+|[^/]+$", "");

      

        
        
        
      

    

You can create a custom EL function that does exactly this:

${f:replaceAll(url, '^[^/]+/+[^/]+|[^/]+$', '')}

      

        
        
        
      

    

To achieve this, first create a class like this:

package com.example;

public final class Functions {
     private Functions() {}

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

      

        
        
        
      

    

and create /WEB-INF/functions.tld

like this:

<?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>matches</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>

      

        
        
        
      

    

which can be imported as:

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