org.omnifaces.util.Xml Maven / Gradle / Ivy
/*
* Copyright OmniFaces
*
* 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.omnifaces.util;
import static java.lang.String.format;
import static java.util.Arrays.asList;
import static java.util.logging.Level.FINE;
import java.io.IOException;
import java.net.URL;
import java.util.ArrayList;
import java.util.List;
import java.util.logging.Logger;
import javax.xml.XMLConstants;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathExpressionException;
import javax.xml.xpath.XPathFactory;
import org.w3c.dom.Document;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException;
/**
*
* Collection of utility methods for the JAXP API in general.
*
*
This class is not listed in showcase! Should I use it?
*
* This class is indeed intented for internal usage only. We won't add methods here on user request. We only add methods
* here once we encounter non-DRY code in OmniFaces codebase. The methods may be renamed/changed without notice.
*
* We don't stop you from using it if you found it in the Javadoc and you think you find it useful, but you have to
* accept the risk that the method signatures can be changed without notice. This utility class exists because OmniFaces
* intends to be free of 3rd party dependencies.
*
* @author Bauke Scholtz
* @since 2.1
*/
public final class Xml {
private static final Logger logger = Logger.getLogger(Xml.class.getName());
// Constructors ---------------------------------------------------------------------------------------------------
private Xml() {
// Hide constructor.
}
// Create ---------------------------------------------------------------------------------------------------------
/**
* Creates a single XML {@link Document} based on given URLs representing XML documents. All those XML documents
* are merged into a single root element named root.
* @param urls The URLs representing XML documents.
* @return A single XML document containing all given XML documents.
* @throws IOException When an I/O error occurs.
* @throws SAXException When a XML parsing error occurs.
*/
public static Document createDocument(List urls) throws IOException, SAXException {
var builder = createDocumentBuilder();
var document = builder.newDocument();
document.appendChild(document.createElement("root"));
parseAndAppendChildren(builder, document, urls);
return document;
}
/**
* Creates an instance of {@link DocumentBuilder} which doesn't validate, nor is namespace aware nor expands entity
* references and disables external entity processing (to keep it as lenient and secure as possible).
* @return A lenient instance of {@link DocumentBuilder}.
*/
public static DocumentBuilder createDocumentBuilder() {
var factory = DocumentBuilderFactory.newInstance();
factory.setValidating(false);
factory.setNamespaceAware(false);
factory.setExpandEntityReferences(false);
try {
factory.setFeature(XMLConstants.FEATURE_SECURE_PROCESSING, true);
unsetAttributeIgnoringIAE(factory, XMLConstants.ACCESS_EXTERNAL_DTD);
unsetAttributeIgnoringIAE(factory, XMLConstants.ACCESS_EXTERNAL_SCHEMA);
return factory.newDocumentBuilder();
}
catch (ParserConfigurationException e) {
throw new UnsupportedOperationException(e);
}
}
private static void unsetAttributeIgnoringIAE(DocumentBuilderFactory factory, String name) {
try {
factory.setAttribute(name, "");
}
catch (IllegalArgumentException e) {
logger.log(FINE, format("Cannot unset attribute '%s'; falling back to default.", name), e);
}
}
// Manipulate -----------------------------------------------------------------------------------------------------
/**
* Parse the given URLs as a document using the given builder and then append all its child nodes to the given
* document.
* @param builder The document builder.
* @param document The document.
* @param urls The URLs representing XML documents.
* @throws IOException When an I/O error occurs.
* @throws SAXException When a XML parsing error occurs.
*/
public static void parseAndAppendChildren(DocumentBuilder builder, Document document, List urls) throws IOException, SAXException {
for (var url : urls) {
if (url == null) {
continue;
}
var connection = url.openConnection();
connection.setUseCaches(false);
try (var input = connection.getInputStream()) {
var children = builder.parse(input).getDocumentElement().getChildNodes();
for (var i = 0; i < children.getLength(); i++) {
document.getDocumentElement().appendChild(document.importNode(children.item(i), true));
}
}
catch (SAXParseException e) {
throw new SAXException("Cannot parse " + url.toExternalForm(), e);
}
}
}
// Traverse -------------------------------------------------------------------------------------------------------
/**
* Convenience method to return a node list matching given XPath expression.
* @param node The node to return node list matching given XPath expression for.
* @param xpath The XPath instance.
* @param expression The XPath expression to match node list.
* @return A node list matching given XPath expression
* @throws XPathExpressionException When the XPath expression contains a syntax error.
*/
public static NodeList getNodeList(Node node, XPath xpath, String expression) throws XPathExpressionException {
return (NodeList) xpath.compile(expression).evaluate(node, XPathConstants.NODESET);
}
/**
* Convenience method to return trimmed text content of given node. This uses
* getFirstChild().getNodeValue() instead of getTextContent() to workaround some buggy
* JAXP implementations.
* @param node The node to return text content for.
* @return Trimmed text content of given node.
*/
public static String getTextContent(Node node) {
return (node.getChildNodes().getLength() == 1 ? node.getFirstChild().getNodeValue() : node.getTextContent()).trim();
}
/**
* Convenience method to return a list of node text contents for given URL representing XML document matching given
* XPath expression.
* @param url The URL representing XML document.
* @param expression The XPath expression to match node list whose text content has to be collected.
* @return A list of node text contents.
* @since 2.6.3
*/
public static List getNodeTextContents(URL url, String expression) {
try {
var nodeList = getNodeList(createDocument(asList(url)).getDocumentElement(), XPathFactory.newInstance().newXPath(), expression);
var nodeTextContents = new ArrayList(nodeList.getLength());
for (var i = 0; i < nodeList.getLength(); i++) {
nodeTextContents.add(getTextContent(nodeList.item(i)));
}
return nodeTextContents;
}
catch (IOException | SAXException | XPathExpressionException e) {
throw new IllegalArgumentException(e);
}
}
}