How can I select an element with multiple classes with Xpath?

Question

In the above xml sample I would like to select all the books that belong to class foo and not in class bar by using xpath.

<?xml version="1.0" encoding="ISO-8859-1"?> <bookstore>   <book class="foo">     <title lang="en">Harry Potter</title>     <author>J K. Rowling</author>     <year>2005</year>     <price>29.99</price>   </book>   <book class="foo bar">     <title lang="en">Harry Potter</title>     <author>J K. Rowling</author>     <year>2005</year>     <price>29.99</price>   </book>   <book class="foo bar">     <title lang="en">Harry Potter</title>     <author>J K. Rowling</author>     <year>2005</year>     <price>29.99</price>   </book> </bookstore> 

Answer 1

By padding the @class value with leading and trailing spaces, you can test for the presence of " foo " and " bar " and not worry about whether it was first, middle, or last, and any false positive hits on "food" or "barren" @class values:

/bookstore/book[contains(concat(' ',@class,' '),' foo ')         and not(contains(concat(' ',@class,' '),' bar '))] 

Answer 2

Although I like Mads solution: Here is another approach for XPath 2.0:

/bookstore/book[                  tokenize(@class," ")="foo"                   and not(tokenize(@class," ")="bar")                ] 

Please note that the following expressions are both true:

("foo","bar")="foo" -> true ("foo","bar")="bar" -> true