Java tutorial
/* * Copyright 2002-2018 the original author or authors. * * Licensed 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 * * https://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. */ package org.springframework.util.xml; import java.util.ArrayList; import java.util.Arrays; import java.util.Collection; import java.util.List; import org.w3c.dom.CharacterData; import org.w3c.dom.Comment; import org.w3c.dom.Element; import org.w3c.dom.EntityReference; import org.w3c.dom.Node; import org.w3c.dom.NodeList; import org.xml.sax.ContentHandler; import org.springframework.lang.Nullable; import org.springframework.util.Assert; /** * Convenience methods for working with the DOM API, * in particular for working with DOM Nodes and DOM Elements. * * @author Juergen Hoeller * @author Rob Harrop * @author Costin Leau * @author Arjen Poutsma * @author Luke Taylor * @since 1.2 * @see org.w3c.dom.Node * @see org.w3c.dom.Element */ public abstract class DomUtils { /** * Retrieves all child elements of the given DOM element that match any of the given element names. * Only looks at the direct child level of the given element; do not go into further depth * (in contrast to the DOM API's {@code getElementsByTagName} method). * @param ele the DOM element to analyze * @param childEleNames the child element names to look for * @return a List of child {@code org.w3c.dom.Element} instances * @see org.w3c.dom.Element * @see org.w3c.dom.Element#getElementsByTagName */ public static List<Element> getChildElementsByTagName(Element ele, String... childEleNames) { Assert.notNull(ele, "Element must not be null"); Assert.notNull(childEleNames, "Element names collection must not be null"); List<String> childEleNameList = Arrays.asList(childEleNames); NodeList nl = ele.getChildNodes(); List<Element> childEles = new ArrayList<>(); for (int i = 0; i < nl.getLength(); i++) { Node node = nl.item(i); if (node instanceof Element && nodeNameMatch(node, childEleNameList)) { childEles.add((Element) node); } } return childEles; } /** * Retrieves all child elements of the given DOM element that match the given element name. * Only look at the direct child level of the given element; do not go into further depth * (in contrast to the DOM API's {@code getElementsByTagName} method). * @param ele the DOM element to analyze * @param childEleName the child element name to look for * @return a List of child {@code org.w3c.dom.Element} instances * @see org.w3c.dom.Element * @see org.w3c.dom.Element#getElementsByTagName */ public static List<Element> getChildElementsByTagName(Element ele, String childEleName) { return getChildElementsByTagName(ele, new String[] { childEleName }); } /** * Utility method that returns the first child element identified by its name. * @param ele the DOM element to analyze * @param childEleName the child element name to look for * @return the {@code org.w3c.dom.Element} instance, or {@code null} if none found */ @Nullable public static Element getChildElementByTagName(Element ele, String childEleName) { Assert.notNull(ele, "Element must not be null"); Assert.notNull(childEleName, "Element name must not be null"); NodeList nl = ele.getChildNodes(); for (int i = 0; i < nl.getLength(); i++) { Node node = nl.item(i); if (node instanceof Element && nodeNameMatch(node, childEleName)) { return (Element) node; } } return null; } /** * Utility method that returns the first child element value identified by its name. * @param ele the DOM element to analyze * @param childEleName the child element name to look for * @return the extracted text value, or {@code null} if no child element found */ @Nullable public static String getChildElementValueByTagName(Element ele, String childEleName) { Element child = getChildElementByTagName(ele, childEleName); return (child != null ? getTextValue(child) : null); } /** * Retrieves all child elements of the given DOM element. * @param ele the DOM element to analyze * @return a List of child {@code org.w3c.dom.Element} instances */ public static List<Element> getChildElements(Element ele) { Assert.notNull(ele, "Element must not be null"); NodeList nl = ele.getChildNodes(); List<Element> childEles = new ArrayList<>(); for (int i = 0; i < nl.getLength(); i++) { Node node = nl.item(i); if (node instanceof Element) { childEles.add((Element) node); } } return childEles; } /** * Extracts the text value from the given DOM element, ignoring XML comments. * <p>Appends all CharacterData nodes and EntityReference nodes into a single * String value, excluding Comment nodes. Only exposes actual user-specified * text, no default values of any kind. * @see CharacterData * @see EntityReference * @see Comment */ public static String getTextValue(Element valueEle) { Assert.notNull(valueEle, "Element must not be null"); StringBuilder sb = new StringBuilder(); NodeList nl = valueEle.getChildNodes(); for (int i = 0; i < nl.getLength(); i++) { Node item = nl.item(i); if ((item instanceof CharacterData && !(item instanceof Comment)) || item instanceof EntityReference) { sb.append(item.getNodeValue()); } } return sb.toString(); } /** * Namespace-aware equals comparison. Returns {@code true} if either * {@link Node#getLocalName} or {@link Node#getNodeName} equals * {@code desiredName}, otherwise returns {@code false}. */ public static boolean nodeNameEquals(Node node, String desiredName) { Assert.notNull(node, "Node must not be null"); Assert.notNull(desiredName, "Desired name must not be null"); return nodeNameMatch(node, desiredName); } /** * Returns a SAX {@code ContentHandler} that transforms callback calls to DOM {@code Node}s. * @param node the node to publish events to * @return the content handler */ public static ContentHandler createContentHandler(Node node) { return new DomContentHandler(node); } /** * Matches the given node's name and local name against the given desired name. */ private static boolean nodeNameMatch(Node node, String desiredName) { return (desiredName.equals(node.getNodeName()) || desiredName.equals(node.getLocalName())); } /** * Matches the given node's name and local name against the given desired names. */ private static boolean nodeNameMatch(Node node, Collection<?> desiredNames) { return (desiredNames.contains(node.getNodeName()) || desiredNames.contains(node.getLocalName())); } }