How to avoid double encoding XML entities with Apache Commons StringEscapeUtils

I was surprised to find that StringEscapeUtils in the Apache Commons Lang library doesn't let you specify whether it should double encode existing XML entities or not. After all, even PHP lets you do this. There is a very simple workaround for that however, so read on.

In PHP if you want to avoid double-encoding you simply pass false to the htmlentities() function like so:

PHP

$strOrig = "&";

$strEnc = htmlentities($strOrig, ENT_XML1, "UTF-8", false);

This will output & instead of &amp; i.e. the string is not double encoded.

To achieve the same result with Java and Apache Commons Lang StringEscapeUtils all you have to do is:

Java

String strOrig = "&";

String strTemp = StringEscapeUtils.unescapeXml(strOrig);

String strEnc = StringEscapeUtils.escapeXml(strTemp);

That's simple after you see it! Just unescape the string first, then escape it. That will take care of any already encoded entities and will avoid double encoding.

-i