How to read namespace from tags using XdmNode?

Question

I wish to read all the namespaces from one tag present in net.sf.saxon.s9api.XdmNode. I'm able to read them using the code below, but due to the performance issue, I should use the existing DOM to parse and read the namespaces.

input.xml

From the above file, I wish to read all the "xmlns" attributes from the link:linkbase tag.

The below code snippet is working as expected but hitting the performance.

Code

private List getNameSpaceListFromFile() throws ValidationException {
    List nsList = new ArrayList();

    try {
        if(inputFile!=null){
            BufferedReader bufferedReader = new BufferedReader(new FileReader(inputFile)); //I18NOK:IOE
            String line;
            StringBuilder stringBuilder = new StringBuilder();

            while((line=bufferedReader.readLine())!= null){
                stringBuilder.append(line.trim());
            }
            XMLStreamReader reader =  XMLInputFactory.newFactory().createXMLStreamReader(new StringReader(stringBuilder.toString().trim().replaceFirst("^([\W]+)<","<"))); /*I18NOK:LSM*/ //removing byte order markers by using "^([\W]+)<","<" 

            while (reader.hasNext()) {
                int event = reader.next();
                if (XMLStreamConstants.START_ELEMENT == event) {
                    if (reader.getNamespaceCount() > 0) {
                        for (int nsIndex = 0; nsIndex < reader.getNamespaceCount(); nsIndex++) {
                            System.out.println(reader.getNamespacePrefix(nsIndex).trim()+"		:		"+ reader.getNamespaceURI(nsIndex).trim());
                            nsList.add(new Namespace(reader.getNamespacePrefix(nsIndex).trim(), reader.getNamespaceURI(nsIndex).trim()));
                        }
                    }
                } 
            }
            bufferedReader.close();
        }
        if(nsList.isEmpty()){
            return new NamespaceLoader(context).getNsListFromProperties();
        }
    } catch (Exception e) {
        e.printStackTrace();
    }
    return nsList;
}

I searched for the proper working solution but could not find any.

Iterator  itemList  = document.axisIterator(Axis.CHILD);
        while(itemList.hasNext()) {
            XdmItem item = itemList.next();
            System.err.println(item.getStringValue());
        }

in above code, I get the full "link" tag in XdmItem but could not find a way to read the linkbase tag and fetch the namespaces.

Any sort of help will be appreciated. also, let me know if any more information is needed.

Michael Kay · Accepted Answer

If I understand correctly, you already have the document held as an instance of XdmNode. If that's the case then you can use the s9api interface to execute the XPath expression

/*/namespace(*)

and this will return a XdmValue containing the list of namespace nodes on the outermost element. You can then just do

for (XdmItem item : result) {
   XdmNode ns = (XdmNode)item;
   String prefix = ns.getNodeName()==null ? "" : ns.getNodeName().getLocalName();
   String uri = ns.getStringValue();
   ...
}

If you prefer you can achieve the same effect by using XdmNode.axisIterator(Axis.CHILD) on the document node to find the outermost element, then XdmNode.axisIterator(Axis.NAMESPACE) to find the namespace nodes.

How to read namespace from tags using XdmNode?

Answers (1)

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