XmlUtils.java

/* 
 * Copyright 2003,2004 Peter Lee, Colin Crist
 *
 * 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 hermes.util;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.StringReader;
import java.io.StringWriter;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;

import org.apache.log4j.Logger;
import org.apache.xml.serialize.OutputFormat;
import org.apache.xml.serialize.XMLSerializer;
import org.w3c.dom.Document;
import org.xml.sax.EntityResolver;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;

/**
 * Utilities for pretty printing XML (uses Apache Xerces).
 */
public abstract class XmlUtils {
	private static final Logger log = Logger.getLogger(XmlUtils.class);

	public static String prettyPrintXml(byte[] bytes) {
		String r = new String(bytes);
		String s = null;

		try {
			s = XmlUtils.prettyPrintXml(r);
		} catch (Exception e) {
			log.error(e.getMessage(), e);
			s = TextUtils.printException(e);
		}

		return s;
	}

	public static String prettyPrintXml(String s) throws IOException, ParserConfigurationException, SAXException {

		if (isXML(s)) {
			StringReader reader = null;
			InputSource source = null;
			String ret = null;

			try {
				reader = new StringReader(s);
				source = new InputSource(reader);
				DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
				factory.setValidating(false);
				factory.setExpandEntityReferences(false);
				factory.setAttribute("http://xml.org/sax/features/external-parameter-entities", false);
				factory.setAttribute("http://apache.org/xml/features/nonvalidating/load-dtd-grammar", false);
				factory.setAttribute("http://apache.org/xml/features/nonvalidating/load-external-dtd", false);
				factory.setAttribute("http://xml.org/sax/features/validation", false);
				DocumentBuilder builder = factory.newDocumentBuilder();

				/**
				 * If we cannot find the DTD or xsd then ignore it and carry on
				 */

				builder.setEntityResolver(new EntityResolver() {
					public InputSource resolveEntity(String publicId, String systemId) {
						InputSource src = new InputSource(systemId);
						try {
							InputStream r = src.getByteStream();
							if (r != null) {
								r.close();
								return src;
							}

						} catch (Exception ex) {
							log.debug(ex.getMessage(), ex) ;
						}
						return new InputSource(new ByteArrayInputStream("<?xml version='1.0' encoding='UTF-8'?>".getBytes())) ;
					}
				});

				Document doc = builder.parse(source);
				ret = prettyPrintXml(doc);
				
			} finally {
				IoUtils.closeQuietly(reader);
			}

			return ret;
		} else {
			return s;
		}
	}

	public static String prettyPrintXml(Document doc) throws IOException {
		StringWriter writer = null;
		String ret = null;

		try {
			writer = new StringWriter();
			OutputFormat format = new OutputFormat(doc);
			format.setLineWidth(80);
			format.setIndenting(true);
			format.setIndent(2);
			XMLSerializer serializer = new XMLSerializer(writer, format);
			serializer.serialize(doc);

			ret = writer.toString();
		} finally {
			IoUtils.closeQuietly(writer);
		}

		return ret;
	}

	public static boolean isXML(final String s) {
		return s != null && (s.startsWith("<?xml") || s.startsWith("<")) ;
	}
}