Gets the child of the specified XML element having the specified name. - Java XML

Java examples for XML:XML Element Child

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Description

Gets the child of the specified XML element having the specified name.

Demo Code

/*/*from www.  ja  v a2 s . c  o m*/
 * Copyright (c) 2009, Red Hat Middleware LLC or third-party contributors as
 * indicated by the @author tags or express copyright attribution
 * statements applied by the authors.  All third-party contributions are
 * distributed under license by Red Hat Middleware LLC.
 *
 * This copyrighted material is made available to anyone wishing to use, modify,
 * copy, or redistribute it subject to the terms and conditions of the GNU
 * Lesser General Public License, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License
 * for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this distribution; if not, write to:
 * Free Software Foundation, Inc.
 * 51 Franklin Street, Fifth Floor
 * Boston, MA  02110-1301  USA
 */
//package com.java2s;
import java.util.ArrayList;
import java.util.Iterator;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;

public class Main {
    /**
     * 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 goodChildren = getChildrenByTagName(element, tagName);

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

    /**
     * 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 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 goodChildren = new ArrayList();
        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();
    }
}

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