XMLUtil.java

/**
 * Copyright 2012 José Martínez
 * 
 * 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 es.udc.pfc.xmpp.xml;

import java.io.StringReader;
import java.io.StringWriter;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.OutputKeys;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerConfigurationException;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMResult;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
import javax.xml.transform.stream.StreamSource;

import org.w3c.dom.Document;
import org.w3c.dom.Element;

/**
 * XML DOM utilities.
 */
public final class XMLUtil {

	private static final DocumentBuilder docBuilder;
	private static final Transformer transformer;

	static {
		try {
			final DocumentBuilderFactory docBuilderFactory = DocumentBuilderFactory.newInstance();
			docBuilderFactory.setIgnoringElementContentWhitespace(true);
			docBuilderFactory.setIgnoringComments(true);

			docBuilder = docBuilderFactory.newDocumentBuilder();
			transformer = TransformerFactory.newInstance().newTransformer();
			transformer.setOutputProperty(OutputKeys.OMIT_XML_DECLARATION, "yes");
			transformer.setOutputProperty(OutputKeys.INDENT, "no");
		} catch (final ParserConfigurationException e) {
			throw new InternalError("Error creating Document Builder");
		} catch (final TransformerConfigurationException e) {
			throw new InternalError("Error creating Transformer");
		}
	}
	
	/**
	 * Returns a new Document from the current DocumentBuidler.
	 * 
	 * @return a new Document
	 */
	public static final Document newDocument() {
		return docBuilder.newDocument();
	}
	
	/**
	 * Parses a String into a new Element.
	 * 
	 * @param element the String to parse
	 * @return the parsed Element
	 */
	public static final Element fromString(final String element) {
		try {
			final Document doc = newDocument();
			transformer.transform(new StreamSource(new StringReader(element)), new DOMResult(doc));
			return doc.getDocumentElement();
		} catch (final TransformerException e) {
			throw new InternalError("Transformer error");
		}
	}
	
	/**
	 * Returns the String representation of an Element.
	 * 
	 * @param element the Element to convert
	 * @return the String representation of a Element
	 */
	public static final String toString(final Element element) {
		try {
			final StringWriter buffer = new StringWriter();
			transformer.transform(new DOMSource(element), new StreamResult(buffer));
			return buffer.toString();
		} catch (final TransformerException e) {
			throw new InternalError("Transformer error");
		}
	}
	
	private XMLUtil() {
	}

}