Spring提供的DomUtils解析工具

/*
* Copyright 2002-2013 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
*
*      http://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.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<Element>();
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
*/
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
*/
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<Element>();
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()));
}

}