setNamespaceContext for default namespace

问题

I have xml as follows. And a default namespace http://september.examples.com/ for

addnumber,firstnumber,secondnumber

XML:

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<soapenv:Body>
<addnumber xmlns="http://september.examples.com/">
<firstnumber>10</firstnumber>
<secondnumber>22</secondnumber>
</addnumber>
</soapenv:Body>
</soapenv:Envelope>

When I try to get value from Xpath using the following code

        factory.setNamespaceAware(true);
        DocumentBuilder builder = factory.newDocumentBuilder();
        Document document = builder.parse(new InputSource(new StringReader(xml)));
        XPathFactory xpathFactory = XPathFactory.newInstance();
        XPath xpath = xpathFactory.newXPath();
        xpath.setNamespaceContext(createContext(xml));
        String value = xpath.compile("/soapenv:Envelope[1]/soapenv:Body[1]/addnumber[1]/firstnumber[1]").evaluate(document).toString();

I'm geting empty value. Since the Xpath I have given here is empty namespace of addnumber[1]/firstnumber[1] How can I give xpath of default namespace?

Note:createContext() will crate a map which would contain prefix, URI

回答1:

You can use any prefix to represent default namespace, as long as it points to the same uri. Simply add another prefix pointing to default namespace uri (http://september.examples.com/) in the function createContext(), and use it in XPath expression.

Related question : https://stackoverflow.com/a/6392700/2998271

回答2:

Unprefixed names in XPath 1.0 always mean "no namespace", this is fixed by the spec:

A QName in the node test is expanded into an expanded-name using the namespace declarations from the expression context. This is the same way expansion is done for element type names in start and end-tags except that the default namespace declared with xmlns is not used: if the QName does not have a prefix, then the namespace URI is null. [my bold]

You must bind a prefix to the http://september.examples.com/ namespace in your context and use that prefix in the XPath expression.

来源：https://stackoverflow.com/questions/22348128/setnamespacecontext-for-default-namespace

标签

java

xml

xpath

namespaces