java - Getting attributes values from a node in XML file -

i have xml file , want values of nodes attributes in it, works efficiently when node usual case of nodes named something:something didn't give me result, null. xml file :

<?xml version="1.0" encoding="utf-8" standalone="yes" ?> <rss version="2.0" xmlns:yweather="http://xml.weather.yahoo.com/ns/rss/1.0" xmlns:geo="http://www.w3.org/2003/01/geo/wgs84_pos#"> <channel>   <title>yahoo! weather - sunnyvale, ca</title>   <link>http://us.rd.yahoo.com/dailynews/rss/weather/sunnyvale__ca/*http://weather.yahoo.com/forecast/usca1116_f.html</link>   <description>yahoo! weather sunnyvale, ca</description>   <language>en-us</language>   <lastbuilddate>fri, 18 dec 2009 9:38 pst</lastbuilddate>   <ttl>60</ttl>   <yweather:location city="sunnyvale" region="ca"   country="united states"/>   <yweather:units temperature="f" distance="mi" pressure="in" speed="mph"/> </channel> </rss> 

the java code :

xpathfactory factory = xpathfactory.newinstance(); xpath xpath = factory.newxpath(); xpathexpression expr = xpath.compile("//rss/@version"); object result = expr.evaluate(doc, xpathconstants.string); system.out.println(result); 

the previous java code works efficiently when replacing //rss/@version //rss/channel/yweather:location/@city returns me null.

first of all, part before : called namespace. quite important concept in xml. retrieve value namespace have make context aware of namespace. can using

xpath.setnamespacecontext(context); 

context must implementation of namespacecontext. in case, namspaces defined within xml might have namespace resolver can namespaces document directly. class doing this:

public class universalnamespaceresolver implements namespacecontext {     private document sourcedocument;      public universalnamespaceresolver(document document) {         sourcedocument = document;     }      public string getnamespaceuri(string prefix) {         if (prefix.equals(xmlconstants.default_ns_prefix)) {             return sourcedocument.lookupnamespaceuri(null);         } else {             return sourcedocument.lookupnamespaceuri(prefix);         }     }      public string getprefix(string namespaceuri) {         return sourcedocument.lookupprefix(namespaceuri);     }      public iterator getprefixes(string namespaceuri) {         return null;     } } 

read more @ http://www.ibm.com/developerworks/library/x-nmspccontext/