XSLT Cookbook

Converting Case

Problem

You want to convert an uppercase string to lowercase or vice versa.

Solution

Use the XSLT translate( ) function. This code, for example, converts from upper- to lowercase:

translate($input,'ABCDEFGHIJKLMNOPQRSTUVWXYZ','abcdefghijklmnopqrstuvwxyz')

This example converts from lower- to uppercase:

translate($input, 'abcdefghijklmnopqrstuvwxyz','ABCDEFGHIJKLMNOPQRSTUVWXYZ')

Discussion

This recipe is, of course, trivial. However, I include it as an opportunity to discuss the solution’s shortcomings. Case conversion is trivial as long as your text is restricted to a single locale. In English, you rarely, if ever, need to deal with special characters containing accents or other complicated case conversions in which a single character must convert to two characters. The most common example is German, in which the lowercase “ß” is converted to an uppercase “SS”. Many modern programming languages provide case-conversion functions that are sensitive to locale, but XSLT does not support this concept directly. This is unfortunate, considering that XSLT has other features supporting internationalization.

A slight improvement can be made by defining general XML entities for each type conversion, as shown in the following example:

<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE stylesheet [ <!ENTITY UPPERCASE "ABCDEFGHIJKLMNOPQRSTUVWXYZ"> <!ENTITY LOWERCASE "abcdefghijklmnopqrstuvwxyz"> <!ENTITY UPPER_TO_LOWER " '&UPPERCASE;' , '&LOWERCASE;' "> <!ENTITY LOWER_TO_UPPER " '&LOWERCASE;' ...