使用XPath检索属性的值

Question

I am trying to retrieve the value of an attribute from an xmel file using XPath and I am not sure where I am going wrong..

This is the XML File

<soapenv:Envelope>
  <soapenv:Header>
    <common:TestInfo testID="PI1" />
  </soapenv:Header>
</soapenv:Envelope>

And this is the code I am using to get the value. Both of these return nothing..

XPathBuilder getTestID = new XPathBuilder("local-name(/*[local-name(.)='Envelope']/*[local-name(.)='Header']/*[local-name(.)='TestInfo'])");
XPathBuilder getTestID2 = new XPathBuilder("Envelope/Header/TestInfo/@testID");

Object doc2 = getTestID.evaluate(context, sourceXML);
Object doc3 = getTestID2.evaluate(context, sourceXML);

How can I retrieve the value of testID?

Answer 1

The XML file you provided does not contain an <Envelope> element, so an expression that requires it will never match.

Post-edit edit

As can be seen from your XML snippet, the document uses a specific namespace for the elements you're trying to match. An XPath engine is namespace-aware, meaning you'll have to ask it exactly what you need. And, keep in mind that a namespace is defined by its uri, not by its abbreviation (so, /namespace:element doesn't do much unless you let the XPath engine know what the namespace namespace refers to).

Answer 2

However you're iterating within the java, your context node is probably not what you think, so remove the "." specifier in your local-name(.) like so:

/*[local-name()='Header']/*[local-name()='TestInfo']/@testID worked fine for me with your XML, although as akaIDIOT says, there isn't an <Envelope> tag to be seen.

Answer 3

If you don't care for the namespaces and use an XPath 2.0 compatible engine, use * for it.

//*:Header/*:TestInfo/@testID

will return the desired input.

It will probably be more elegant to register the needed namespaces (not covered here, depends on your XPath engine) and query using these:

//soapenv:Header/common:TestInfo/@testID

Answer 4

Your first XPath has an extra local-name() wrapped around the whole thing:

local-name(/*[local-name(.)='Envelope']/*[local-name(.)='Header']
                                                         /*[local-name(.)='TestInfo'])

The result of this XPath will either be the string value "TestInfo" if the TestInfo node is found, or a blank string if it is not.

If your XML is structured like you say it is, then this should work:

/*[local-name()='Envelope']/*[local-name()='Header']/*[local-name()='TestInfo']/@testID

But preferably, you should be working with namespaces properly instead of (ab)using local-name() . I have a post here that shows how to do this in Java.