问题:

What is the XPath to find only ONE node (whichever) having a certain attribute (actually I'm interested in the attribute, not the node). For example, in my XML, I have several tags having a lang attribute. I know all of them must have the same value. I just want to get any of them.

Right now, I do this : //*[1][@lang]/@lang, but it seems not to work properly, for an unknown reason.

My tries have led me to things ranging from concatenation of all the @lang values ('en en en en...') to nothing, with sometimes inbetween what I want but not on all XML.

EDIT :

Actually //@lang[1] can not work, because the function position() is called before the test on a lang attribute presence. So it always takes the very first element found in the XML. It worked best at the time because many many times, the lang attribute was on root element.

回答1:

After some more tackling, here is a working solution :

 (//@lang)[1]

Parentheses are needed to separate the [1] from the attribute name, otherwise the position() function is applied within the parent element of the attribute (which is useless since there can be only one attribute of a certain name within a tag : that's why //@lang[2] always selects nothing).