XOM API for Processing XML with Java

[Laurent Bihanic <laurent.bihanic AT atosorigin.com>]

Hi,

I need to pre-process an XML document to add some information to it. The 
elements to be added shall belong to a known namespace, already defined in the 
document. I want to avoid re-declaring this namespace with a new prefix and 
thus I need to retrieve the namespace prefix knowing the URI.

I found no way in XOM to do this but found a solution using XPath. Yet, it 
would be nice for XOM to provide a "native" solution.

I'm proposing to add a new getNamespacePrefix(String uri) method to Element 
(see below for a possible implementation). I tested it and it works fine once 
the getNamespaceURI bug I reported earlier fixed.

    public String getNamespacePrefix(String uri) {
        if ((uri == null) || (uri.length() == 0)) {
            throw new IllegalArgumentException("uri");
        }

        // Check node own namespace first.
        if (uri.equals(this.getNamespaceURI())) {
            return this.getNamespacePrefix();
        }

        // Check default namespace in scope.
        if (uri.equals(this.getNamespaceURI(null))) {
            return "";
        }

        // Search ancestor-or-self nodes for namespace declaration.
        Element current = this;
        while (current != null) {
            prefix = current.getNamespacePrefix();

            if ((prefix != null) && (prefix.length() != 0) &&
                                    (uri.equals(current.getNamespaceURI()))) {
                return prefix;
            }

            int max = current.getNamespaceDeclarationCount();
            for (int i=0; i<max; i++) {
                prefix = current.getNamespacePrefix(i);

                if ((prefix != null) && (prefix.length() != 0) &&
                            (uri.equals(current.getNamespaceURI(prefix)))) {
                    return prefix;
                }
            }
            ParentNode parent = current.getParent();
            current = (parent instanceof Element)? (Element)parent: null;
        }
        return null;
    }

Laurent