Parsing XML with default namespace using xPath in javascript

Question

I need to create an XML xPath parser. All parsing has to happen on client side (using javascript). I created an javascript that does this, and everything looks OK until default namespaces come into play. I simply can't query XML that has default namespace.

I created an example code on fiddle. In xmlString is XML string received from server. In xPathString is query done on received XML.

Here are some scenarios:

http://jsfiddle.net/BF34q/1/ - no namespaces - everything works OK
http://jsfiddle.net/BF34q/2/ - ns namespace added. element has ns: prefix. xPath uses this prefix - OK
http://jsfiddle.net/BF34q/3/ - default namespace used - not sure how to configure xPathString.

Note that others will use this parser, so I would really like to avoid solutions like

var xPathString = "//*[local-name()='book']";

and enable them to parse it using simple xPath expressions. I wonder if it is possible to assign default namespace prefix in javascript?

Note: The example provided on fiddle will not work in IE.

dugokontov · Accepted Answer · 2011-07-27 10:45:57Z

10

I think there are three ways to do this:

Use //*[local-name()='book'] syntax for accessing nodes
Convert XML to string, remove default namespace using RegExp, convert it back to XML
For XML files where you know namespaces in advance, you can create your own namespace resolver, which will allow you to use your own prefix for default namespace.

This can be achieved like this:

function nsResolver(prefix) {
    switch (prefix) {
        case 'xhtml':
            return 'http://www.w3.org/1999/xhtml';
        case 'mathml':
            return 'http://www.w3.org/1998/Math/MathML';
        default:
            return 'http://example.com/domain';
    }
}
xml.evaluate('//myPrefix:book', xml, nsResolver, XPathResult.ANY_TYPE, null);

answered Jul 27, 2011 at 10:45

dugokontov

4,6721 gold badge27 silver badges26 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Community · Accepted Answer · 2017-05-23 12:23:10Z

0

I've got the impression that your understanding of the XPath processing doesn't match the implementation - unless, that is, the implementation you're dealing with is very different from the ones I'm familiar with.

Usually, the XPath processor has to have namespaces registered and prefixes mapped to them in order for the expression to be successfully evaluated. So the prefixes could be anything - the only thing that matters is what they're mapped to. See this answer by a known expert to get more information.

edited May 23, 2017 at 12:23

CommunityBot

11 silver badge

answered Jul 20, 2011 at 12:23

Lumi

15.5k9 gold badges64 silver badges93 bronze badges

5 Comments

dugokontov Over a year ago

You can omit prefix for namespace, and then that namespace is considered default namespace. Here are some examples and clarifications: w3schools.com/xml/xml_namespaces.asp, developerfusion.com/article/3720/understanding-xml-namespaces/5

Lumi Over a year ago

@dugokontov, I think you're confusing no namespace and default namespace. In an XML doc, you set the default namespace using xmlns="something", so without a prefix. By default, the default namespace is the empty namespace (no namespace). The default namespace depends on the context; XPath makes no exception here. By not specifying any prefix with his XPath expressions and not registering any namespaces, the OP's expression very likely matches nodes in no namespace.

dugokontov Over a year ago

you just sad the same thing as I did in my comment: In an XML doc, you set the default namespace using xmlns="something", so without a prefix == You can omit prefix for namespace, and then that namespace is considered default namespace. Also, your scenario in your last sentence is described in my fist example provided: jsfiddle.net/BF34q/1. So, I'm little confused what do you want to say to me?

Lumi Over a year ago

@dugokontov, I can see why you're confused :-) I must have misread your statement, sorry for that. What I want to say to you is that you need to register the namespace http://example.com/domain with your XPath processor. Just map it to some prefix x and then use that prefix with your query. It'll work using libraries such as LibXML2. Not sure what the incantation for the processor that's embedded in the browser should be, though. Maybe try using the Saxon library.

dugokontov Over a year ago

don't get me wrong, but I have feeling that you haven't read my question at all. I know I have to assign some prefix to default namespace, and my question was I wonder if it is possible to assign default namespace prefix in javascript?. Plz read before answering...

Collectives™ on Stack Overflow

Parsing XML with default namespace using xPath in javascript

2 Answers 2

Comments

5 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

5 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related