Get the content of an optional child element : DOM Element « XML « Java

1. Java
2. XML
3. DOM Element

Get the content of an optional child element

    

import java.util.ArrayList;
import java.util.Iterator;

import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;

/**
 * A utility class to cover up the rough bits of xml parsing
 * 
 * @author <a href="mailto:chris@kimptoc.net">Chris Kimpton</a>
 * @version $Revision: 70500 $
 */
public class XmlHelper {

  /**
   * Macro to get the content of an optional child element.
   * 
   * @param element
   *          The parent element.
   * @param tagName
   *          The name of the desired child.
   * @return The element content or null.
   */
  public static String getOptionalChildContent(Element element, String tagName) throws Exception {
    return getElementContent(getOptionalChild(element, tagName));
  }

  public static boolean getOptionalChildBooleanContent(Element element, String name)
      throws Exception {
    Element child = getOptionalChild(element, name);
    if (child != null) {
      String value = getElementContent(child).toLowerCase();
      return value.equals("true") || value.equals("yes");
    }

    return false;
  }

  /**
   * Returns an iterator over the children of the given element with the given
   * tag name.
   * 
   * @param element
   *          The parent element
   * @param tagName
   *          The name of the desired child
   * @return An interator of children or null if element is null.
   */
  public static Iterator<Element> getChildrenByTagName(Element element, String tagName) {
    if (element == null)
      return null;
    // getElementsByTagName gives the corresponding elements in the whole
    // descendance. We want only children

    NodeList children = element.getChildNodes();
    ArrayList<Element> goodChildren = new ArrayList<Element>();
    for (int i = 0; i < children.getLength(); i++) {
      Node currentChild = children.item(i);
      if (currentChild.getNodeType() == Node.ELEMENT_NODE
          && ((Element) currentChild).getTagName().equals(tagName)) {
        goodChildren.add((Element) currentChild);
      }
    }
    return goodChildren.iterator();
  }

  /**
   * Gets the child of the specified element having the specified unique name.
   * If there are more than one children elements with the same name and
   * exception is thrown.
   * 
   * @param element
   *          The parent element
   * @param tagName
   *          The name of the desired child
   * @return The named child.
   * 
   * @throws Exception
   *           Child was not found or was not unique.
   */
  public static Element getUniqueChild(Element element, String tagName) throws Exception {
    Iterator<Element> goodChildren = getChildrenByTagName(element, tagName);

    if (goodChildren != null && goodChildren.hasNext()) {
      Element child = goodChildren.next();
      if (goodChildren.hasNext()) {
        throw new Exception("expected only one " + tagName + " tag");
      }
      return child;
    } else {
      throw new Exception("expected one " + tagName + " tag");
    }
  }

  /**
   * Gets the child of the specified element having the specified name. If the
   * child with this name doesn't exist then null is returned instead.
   * 
   * @param element
   *          the parent element
   * @param tagName
   *          the name of the desired child
   * @return either the named child or null
   */
  public static Element getOptionalChild(Element element, String tagName) throws Exception {
    return getOptionalChild(element, tagName, null);
  }

  /**
   * Gets the child of the specified element having the specified name. If the
   * child with this name doesn't exist then the supplied default element is
   * returned instead.
   * 
   * @param element
   *          the parent element
   * @param tagName
   *          the name of the desired child
   * @param defaultElement
   *          the element to return if the child doesn't exist
   * @return either the named child or the supplied default
   */
  public static Element getOptionalChild(Element element, String tagName, Element defaultElement)
      throws Exception {
    Iterator<Element> goodChildren = getChildrenByTagName(element, tagName);

    if (goodChildren != null && goodChildren.hasNext()) {
      Element child = goodChildren.next();
      if (goodChildren.hasNext()) {
        throw new Exception("expected only one " + tagName + " tag");
      }
      return child;
    } else {
      return defaultElement;
    }
  }

  /**
   * Get the content of the given element.
   * 
   * @param element
   *          The element to get the content for.
   * @return The content of the element or null.
   */
  public static String getElementContent(final Element element) throws Exception {
    return getElementContent(element, null);
  }

  /**
   * Get the content of the given element.
   * 
   * @param element
   *          The element to get the content for.
   * @param defaultStr
   *          The default to return when there is no content.
   * @return The content of the element or the default.
   */
  public static String getElementContent(Element element, String defaultStr) throws Exception {
    if (element == null)
      return defaultStr;

    NodeList children = element.getChildNodes();
    String result = "";
    for (int i = 0; i < children.getLength(); i++) {
      if (children.item(i).getNodeType() == Node.TEXT_NODE
          || children.item(i).getNodeType() == Node.CDATA_SECTION_NODE) {
        result += children.item(i).getNodeValue();
      } else if (children.item(i).getNodeType() == Node.COMMENT_NODE) {
        // Ignore comment nodes
      }
    }
    return result.trim();
  }

  /**
   * Macro to get the content of a unique child element.
   * 
   * @param element
   *          The parent element.
   * @param tagName
   *          The name of the desired child.
   * @return The element content or null.
   */
  public static String getUniqueChildContent(Element element, String tagName) throws Exception {
    return getElementContent(getUniqueChild(element, tagName));
  }

}

   
    
    
    
  

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