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DSpace core data model and service APIs.
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/**
 * The contents of this file are subject to the license and copyright
 * detailed in the LICENSE and NOTICE files at the root of the source
 * tree and available online at
 *
 * http://www.dspace.org/license/
 */
package org.dspace.app.util;

import java.util.ArrayList;
import java.util.List;

import org.apache.commons.lang3.StringUtils;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;

/**
 * Simple class to read information from small XML using DOM manipulation
 *
 * @author Andrea Bollini
 */
public class XMLUtils {

    /**
     * Default constructor
     */
    private XMLUtils() { }

    /**
     * @param dataRoot the starting node
     * @param name     the tag name of the child element to find.
     * @return the list of all DOM Element with the provided name direct child
     * of the starting node
     */
    public static List getElementList(Element dataRoot, String name) {
        NodeList list = dataRoot.getElementsByTagName(name);
        List listElements = new ArrayList<>();
        for (int i = 0; i < list.getLength(); i++) {
            Element item = (Element) list.item(i);
            if (item.getParentNode().equals(dataRoot)) {
                listElements.add(item);
            }
        }
        return listElements;
    }

    /**
     * @param dataRoot the starting node
     * @param name     the name of the sub element
     * @param attr     the attribute to get
     * @return the value of the attribute for the sub element with the specified
     * name in the starting node
     */
    public static String getElementAttribute(Element dataRoot, String name,
                                             String attr) {
        Element element = getSingleElement(dataRoot, name);
        String attrValue = null;
        if (element != null) {
            attrValue = element.getAttribute(attr);
            if (StringUtils.isNotBlank(attrValue)) {
                attrValue = attrValue.trim();
            } else {
                attrValue = null;
            }
        }
        return attrValue;
    }

    /**
     * @param dataRoot the starting node
     * @param name     the name of the sub element
     * @return the text content of the sub element with the specified name in
     * the starting node
     */
    public static String getElementValue(Element dataRoot, String name) {
        Element element = getSingleElement(dataRoot, name);
        String elementValue = null;
        if (element != null) {
            elementValue = element.getTextContent();
            if (StringUtils.isNotBlank(elementValue)) {
                elementValue = elementValue.trim();
            } else {
                elementValue = null;
            }
        }
        return elementValue;
    }

    /**
     * Return the first element child with the specified name
     *
     * @param dataRoot the starting node
     * @param name     the name of sub element to look for
     * @return the first child element or null if no present
     */
    public static Element getSingleElement(Element dataRoot, String name) {
        List nodeList = getElementList(dataRoot, name);
        Element element = null;
        if (nodeList != null && nodeList.size() > 0) {
            element = (Element) nodeList.get(0);
        }
        return element;
    }

    /**
     * @param rootElement    the starting node
     * @param subElementName the tag name of the child element to find.
     * @return a list of string including all the text contents of the sub
     * element with the specified name. If there are not sub element
     * with the supplied name the method will return null
     */
    public static List getElementValueList(Element rootElement,
                                                   String subElementName) {
        if (rootElement == null) {
            return null;
        }

        List subElements = getElementList(rootElement, subElementName);
        if (subElements == null) {
            return null;
        }

        List result = new ArrayList<>();
        for (Element el : subElements) {
            if (StringUtils.isNotBlank(el.getTextContent())) {
                result.add(el.getTextContent().trim());
            }
        }
        return result;
    }

    /**
     * root/subElement[]/field1, field2, fieldN
     *
     * @param rootElement    the starting node
     * @param subElementName the name of the sub element to work on
     * @param fieldsName     the names of the sub-sub-elements from which get the text
     *                       content
     * @return a list of array strings. The length of the array is equals to the
     * number of fields required. For any fields the first textual value
     * found in the sub element is used, null if no value is present
     */
    public static List getElementValueArrayList(Element rootElement,
                                                          String subElementName, String... fieldsName) {
        if (rootElement == null) {
            return null;
        }

        List subElements = getElementList(rootElement, subElementName);
        if (subElements == null) {
            return null;
        }

        List result = new ArrayList<>();
        for (Element el : subElements) {
            String[] tmp = new String[fieldsName.length];
            for (int idx = 0; idx < fieldsName.length; idx++) {
                tmp[idx] = XMLUtils.getElementValue(el, fieldsName[idx]);
            }
            result.add(tmp);
        }
        return result;
    }
}