XmlHelper.java Source code

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Here is the source code for XmlHelper.java

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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));
    }

}