Get all prefixes defined, up to the root, for a namespace URI. : Namespace « XML « Java Tutorial

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/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied. See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

import java.util.List;

import javax.xml.XMLConstants;

import org.w3c.dom.Element;
import org.w3c.dom.NamedNodeMap;
import org.w3c.dom.Node;
/**
 * Few simple utils to read DOM. This is originally from the Jakarta Commons Modeler.
 * 
 * @author Costin Manolache
 */
public class Utils {
  private static final String XMLNAMESPACE = "xmlns";
  /**
   * Get all prefixes defined, up to the root, for a namespace URI.
   * 
   * @param element
   * @param namespaceUri
   * @param prefixes
   */
  public static void getPrefixesRecursive(Element element, String namespaceUri, List<String> prefixes) {
      getPrefixes(element, namespaceUri, prefixes);
      Node parent = element.getParentNode();
      if (parent instanceof Element) {
          getPrefixesRecursive((Element)parent, namespaceUri, prefixes);
      }
  }
  /**
   * Get all prefixes defined on this element for the specified namespace.
   * 
   * @param element
   * @param namespaceUri
   * @param prefixes
   */
  public static void getPrefixes(Element element, String namespaceUri, List<String> prefixes) {
      NamedNodeMap atts = element.getAttributes();
      for (int i = 0; i < atts.getLength(); i++) {
          Node node = atts.item(i);
          String name = node.getNodeName();
          if (namespaceUri.equals(node.getNodeValue())
              && (name != null && (XMLNAMESPACE.equals(name) || name.startsWith(XMLNAMESPACE + ":")))) {
              prefixes.add(node.getPrefix());
          }
      }
  }
}