Java: Stripping namespaces from XML using DOM

Although we usually like to enforce strict rules on our data, sometimes we just like to loosen it up a little. Don't get me wrong, namespaces definitely have a place and we use them to enforce contracts on our data. But sometimes, we don't need (and thus, want) that layer of complexity.

The solution

It took me a while to understand why it isn't possible to just unset the namespace for an XML node. Since a namespace is an integral part of a node's qualified name, node A with namespace XYZ is really a different entity than node A with namespace ABC. Thus, we need to rename the node. The Document (org.w3c.dom.Document) class conveniently provides a method renameNode(Node n, String namespaceURI, String qualifiedName). Supplying null as namespaceURI effectively removes the namespace for the node. You'll probably want to apply the change to your entire subtree, so it should be recursive:

import org.w3c.dom.Document;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
 
...
 
/**
  * Recursively renames the namespace of a node.
  * @param node the starting node.
  * @param namespace the new namespace. Supplying <tt>null</tt> removes the namespace.
 */
publicstatic void renameNamespaceRecursive(Node node, String namespace) {
     Document document = node.getOwnerDocument();
     if (node.getNodeType() == Node.ELEMENT_NODE) {
         document.renameNode(node, namespace, node.getNodeName());
    }
    NodeList list = node.getChildNodes();
    for(int i = 0; i < list.getLength(); ++i) {
         renameNamespaceRecursive(list.item(i), namespace);
    }

Why share this?

Recently I read about the Rule of Three, which led me to believe I should share this solution. Here are the three problems I solved using it:

• Interacting with a (legacy) component which uses a different namespace, or none at all.
• Pretty-print XML snippets without cluttering it with namespaces.
• Extracting HTML snippets embedded in an XML document.

References

• Rule of Three, Jeff Atwood
  http://www.codinghorror.com/blog/2013/07/rule-of-three.html