Compare two DOM Nodes : Node « 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.ArrayList;
import java.util.List;

import org.w3c.dom.Attr;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NamedNodeMap;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.w3c.dom.Text;

/**
 * @version $Rev: 514087 $ $Date: 2007-03-03 01:13:40 -0500 (Sat, 03 Mar 2007) $
 */
public class DOMUtils {
  private static void trimEmptyTextNodes(Node node) {
    Element element = null;
    if (node instanceof Document) {
      element = ((Document) node).getDocumentElement();
    } else if (node instanceof Element) {
      element = (Element) node;
    } else {
      return;
    }

    List<Node> nodesToRemove = new ArrayList<Node>();
    NodeList children = element.getChildNodes();
    for (int i = 0; i < children.getLength(); i++) {
      Node child = children.item(i);
      if (child instanceof Element) {
        trimEmptyTextNodes(child);
      } else if (child instanceof Text) {
        Text t = (Text) child;
        if (t.getData().trim().length() == 0) {
          nodesToRemove.add(child);
        }
      }
    }

    for (Node n : nodesToRemove) {
      element.removeChild(n);
    }
  }

  public static void compareNodes(Node expected, Node actual, boolean trimEmptyTextNodes)
      throws Exception {
    if (trimEmptyTextNodes) {
      trimEmptyTextNodes(expected);
      trimEmptyTextNodes(actual);
    }
    compareNodes(expected, actual);
  }

  public static void compareNodes(Node expected, Node actual) throws Exception {
    if (expected.getNodeType() != actual.getNodeType()) {
      throw new Exception("Different types of nodes: " + expected + " " + actual);
    }
    if (expected instanceof Document) {
      Document expectedDoc = (Document) expected;
      Document actualDoc = (Document) actual;
      compareNodes(expectedDoc.getDocumentElement(), actualDoc.getDocumentElement());
    } else if (expected instanceof Element) {
      Element expectedElement = (Element) expected;
      Element actualElement = (Element) actual;

      // compare element names
      if (!expectedElement.getLocalName().equals(actualElement.getLocalName())) {
        throw new Exception("Element names do not match: " + expectedElement.getLocalName() + " "
            + actualElement.getLocalName());
      }
      // compare element ns
      String expectedNS = expectedElement.getNamespaceURI();
      String actualNS = actualElement.getNamespaceURI();
      if ((expectedNS == null && actualNS != null)
          || (expectedNS != null && !expectedNS.equals(actualNS))) {
        throw new Exception("Element namespaces names do not match: " + expectedNS + " " + actualNS);
      }

      String elementName = "{" + expectedElement.getNamespaceURI() + "}"
          + actualElement.getLocalName();

      // compare attributes
      NamedNodeMap expectedAttrs = expectedElement.getAttributes();
      NamedNodeMap actualAttrs = actualElement.getAttributes();
      if (countNonNamespaceAttribures(expectedAttrs) != countNonNamespaceAttribures(actualAttrs)) {
        throw new Exception(elementName + ": Number of attributes do not match up: "
            + countNonNamespaceAttribures(expectedAttrs) + " "
            + countNonNamespaceAttribures(actualAttrs));
      }
      for (int i = 0; i < expectedAttrs.getLength(); i++) {
        Attr expectedAttr = (Attr) expectedAttrs.item(i);
        if (expectedAttr.getName().startsWith("xmlns")) {
          continue;
        }
        Attr actualAttr = null;
        if (expectedAttr.getNamespaceURI() == null) {
          actualAttr = (Attr) actualAttrs.getNamedItem(expectedAttr.getName());
        } else {
          actualAttr = (Attr) actualAttrs.getNamedItemNS(expectedAttr.getNamespaceURI(),
              expectedAttr.getLocalName());
        }
        if (actualAttr == null) {
          throw new Exception(elementName + ": No attribute found:" + expectedAttr);
        }
        if (!expectedAttr.getValue().equals(actualAttr.getValue())) {
          throw new Exception(elementName + ": Attribute values do not match: "
              + expectedAttr.getValue() + " " + actualAttr.getValue());
        }
      }

      // compare children
      NodeList expectedChildren = expectedElement.getChildNodes();
      NodeList actualChildren = actualElement.getChildNodes();
      if (expectedChildren.getLength() != actualChildren.getLength()) {
        throw new Exception(elementName + ": Number of children do not match up: "
            + expectedChildren.getLength() + " " + actualChildren.getLength());
      }
      for (int i = 0; i < expectedChildren.getLength(); i++) {
        Node expectedChild = expectedChildren.item(i);
        Node actualChild = actualChildren.item(i);
        compareNodes(expectedChild, actualChild);
      }
    } else if (expected instanceof Text) {
      String expectedData = ((Text) expected).getData().trim();
      String actualData = ((Text) actual).getData().trim();

      if (!expectedData.equals(actualData)) {
        throw new Exception("Text does not match: " + expectedData + " " + actualData);
      }
    }
  }

  private static int countNonNamespaceAttribures(NamedNodeMap attrs) {
    int n = 0;
    for (int i = 0; i < attrs.getLength(); i++) {
      Attr attr = (Attr) attrs.item(i);
      if (!attr.getName().startsWith("xmlns")) {
        n++;
      }
    }
    return n;
  }

}