jeeves.utils.Xml.java Source code

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//=============================================================================
//===   Copyright (C) 2001-2005 Food and Agriculture Organization of the
//===   United Nations (FAO-UN), United Nations World Food Programme (WFP)
//===   and United Nations Environment Programme (UNEP)
//===
//===   This library is free software; you can redistribute it and/or
//===   modify it under the terms of the GNU Lesser General Public
//===   License as published by the Free Software Foundation; either
//===   version 2.1 of the License, or (at your option) any later version.
//===
//===   This library is distributed in the hope that it will be useful,
//===   but WITHOUT ANY WARRANTY; without even the implied warranty of
//===   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
//===   Lesser General Public License for more details.
//===
//===   You should have received a copy of the GNU Lesser General Public
//===   License along with this library; if not, write to the Free Software
//===   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
//===
//===   Contact: Jeroen Ticheler - FAO - Viale delle Terme di Caracalla 2,
//===   Rome - Italy. email: GeoNetwork@fao.org
//==============================================================================

package jeeves.utils;

import jeeves.exceptions.XSDValidationErrorEx;
import net.sf.json.JSON;
import net.sf.json.xml.XMLSerializer;
import net.sf.saxon.Configuration;
import net.sf.saxon.FeatureKeys;

import org.apache.commons.io.IOUtils;
import org.apache.commons.lang.SystemUtils;
import org.apache.fop.apps.Fop;
import org.apache.fop.apps.FopFactory;
import org.apache.fop.apps.MimeConstants;
import org.apache.xml.resolver.tools.CatalogResolver;
import org.jdom.DocType;
import org.jdom.Document;
import org.jdom.Element;
import org.jdom.JDOMException;
import org.jdom.Namespace;
import org.jdom.input.SAXBuilder;
import org.jdom.output.Format;
import org.jdom.output.SAXOutputter;
import org.jdom.output.XMLOutputter;
import org.jdom.transform.JDOMResult;
import org.jdom.transform.JDOMSource;
import org.jdom.xpath.XPath;
import org.mozilla.universalchardet.UniversalDetector;
import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException;
import org.xml.sax.helpers.DefaultHandler;

import javax.xml.XMLConstants;
import javax.xml.transform.Result;
import javax.xml.transform.Source;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.URIResolver;
import javax.xml.transform.sax.SAXResult;
import javax.xml.transform.stream.StreamResult;
import javax.xml.transform.stream.StreamSource;
import javax.xml.validation.Schema;
import javax.xml.validation.SchemaFactory;
import javax.xml.validation.ValidatorHandler;
import java.io.BufferedOutputStream;
import java.io.ByteArrayInputStream;
import java.io.DataInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintStream;
import java.io.PrintWriter;
import java.io.StringReader;
import java.io.UnsupportedEncodingException;
import java.lang.reflect.Method;
import java.net.HttpURLConnection;
import java.net.URI;
import java.net.URISyntaxException;
import java.net.URL;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.charset.CharacterCodingException;
import java.nio.charset.Charset;
import java.nio.charset.CharsetDecoder;
import java.nio.charset.CharsetEncoder;
import org.eclipse.core.runtime.URIUtil;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.UUID;

//=============================================================================

/**
 *  General class of useful static methods.
 */
public final class Xml {

    public static final Namespace xsiNS = Namespace.getNamespace("xsi",
            XMLConstants.W3C_XML_SCHEMA_INSTANCE_NS_URI);

    //--------------------------------------------------------------------------

    /**
     *
     * @param validate
     * @return
     */
    private static SAXBuilder getSAXBuilder(boolean validate) {
        SAXBuilder builder = getSAXBuilderWithoutXMLResolver(validate);
        Resolver resolver = ResolverWrapper.getInstance();
        builder.setEntityResolver(resolver.getXmlResolver());
        return builder;
    }

    private static SAXBuilder getSAXBuilderWithoutXMLResolver(boolean validate) {
        SAXBuilder builder = new JeevesSAXBuilder(validate);
        //SAXBuilder builder = new SAXBuilder(validate);
        builder.setFeature(XMLConstants.FEATURE_SECURE_PROCESSING, true);
        return builder;
    }

    //--------------------------------------------------------------------------

    /**
     *
     */
    public static void resetResolver() {
        Resolver resolver = ResolverWrapper.getInstance();
        resolver.reset();
    }

    //--------------------------------------------------------------------------
    //---
    //--- Load API
    //---
    //--------------------------------------------------------------------------

    /**
     *
     * @param file
     * @return
     * @throws IOException
     * @throws JDOMException
     */
    public static Element loadFile(String file) throws IOException, JDOMException {
        return loadFile(new File(file));
    }

    //--------------------------------------------------------------------------

    /**
     * Loads an xml file from a URL and returns its root node.
     *
     * @param url
     * @return
     * @throws IOException
     * @throws JDOMException
     */
    public static Element loadFile(URL url) throws IOException, JDOMException {
        SAXBuilder builder = getSAXBuilderWithoutXMLResolver(false);//new SAXBuilder();
        Document jdoc = builder.build(url);

        return (Element) jdoc.getRootElement().detach();
    }

    //--------------------------------------------------------------------------

    /**
     * Loads an xml file from a URL after posting content to the URL.
     *
     * @param url
     * @param xmlQuery
     * @return
     * @throws IOException
     * @throws JDOMException
     */
    public static Element loadFile(URL url, Element xmlQuery) throws IOException, JDOMException {
        Element result = null;
        try {
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            connection.setRequestMethod("POST");
            connection.setRequestProperty("Content-Type", "application/xml");
            connection.setRequestProperty("Content-Length",
                    "" + Integer.toString(getString(xmlQuery).getBytes("UTF-8").length));
            connection.setRequestProperty("Content-Language", "en-US");
            connection.setDoOutput(true);
            PrintStream out = new PrintStream(connection.getOutputStream(), true, "UTF-8");
            out.print(getString(xmlQuery));
            out.close();

            SAXBuilder builder = getSAXBuilderWithoutXMLResolver(false);//new SAXBuilder();
            Document jdoc = builder.build(connection.getInputStream());

            result = (Element) jdoc.getRootElement().detach();
        } catch (Exception e) {
            Log.error(Log.ENGINE, "Error loading URL " + url.getPath() + " .Threw exception " + e);
            e.printStackTrace();
        }
        return result;
    }

    //--------------------------------------------------------------------------

    /**
     * Loads an xml file and returns its root node.
     *
     * @param file
     * @return
     * @throws IOException
     * @throws JDOMException
     */
    public static Element loadFile(File file) throws IOException, JDOMException {
        SAXBuilder builder = getSAXBuilderWithoutXMLResolver(false); //new SAXBuilder();

        String convert = System.getProperty("jeeves.filecharsetdetectandconvert");

        // detect charset and convert if required
        if (convert != null && convert.equals("enabled")) {
            byte[] content = convertFileToUTF8ByteArray(file);
            return loadStream(new ByteArrayInputStream(content));

            // no charset detection and conversion allowed
        } else {
            Document jdoc = builder.build(file);
            return (Element) jdoc.getRootElement().detach();
        }

    }

    //--------------------------------------------------------------------------

    /**
     * Reads file into byte array, detects charset and converts from this  
       * charset to UTF8
     *
     * @param file file to decode and convert to UTF8
     * @return
     * @throws IOException
     * @throws CharacterCodingException
     */

    public synchronized static byte[] convertFileToUTF8ByteArray(File file)
            throws IOException, CharacterCodingException {
        FileInputStream in = null;
        DataInputStream inStream = null;
        try {
            in = new FileInputStream(file);
            inStream = new DataInputStream(in);
            byte[] buf = new byte[(int) file.length()];
            int nrRead = inStream.read(buf);

            UniversalDetector detector = new UniversalDetector(null);
            detector.handleData(buf, 0, nrRead);
            detector.dataEnd();

            String encoding = detector.getDetectedCharset();
            detector.reset();
            if (encoding != null) {
                if (!encoding.equals("UTF-8")) {
                    Log.error(Log.JEEVES, "Detected character set " + encoding + ", converting to UTF-8");
                    return convertByteArrayToUTF8ByteArray(buf, encoding);
                }
            }
            return buf;
        } finally {
            if (in != null) {
                IOUtils.closeQuietly(in);
            }
            if (inStream != null) {
                IOUtils.closeQuietly(inStream);
            }
        }
    }

    //--------------------------------------------------------------------------

    /**
     * Decode byte array as specified charset, then convert to UTF-8 
       * by encoding as UTF8
     *
     * @param buf byte array to decode and convert to UTF8
     * @param charsetName charset to decode byte array into
     * @return
     * @throws CharacterCodingException
     */

    public synchronized static byte[] convertByteArrayToUTF8ByteArray(byte[] buf, String charsetName)
            throws CharacterCodingException {
        Charset cset;
        cset = Charset.forName(charsetName); // detected character set name
        CharsetDecoder csetDecoder = cset.newDecoder();

        Charset utf8 = Charset.forName("UTF-8");
        CharsetEncoder utf8Encoder = utf8.newEncoder();

        ByteBuffer inputBuffer = ByteBuffer.wrap(buf);

        // decode as detected character set
        CharBuffer data = csetDecoder.decode(inputBuffer);

        // encode as UTF-8
        ByteBuffer outputBuffer = utf8Encoder.encode(data);

        // remove any nulls from the end of the encoded data why? - this is a 
        // bug in the encoder???? could also be that the file has characters
        // from more than one charset?
        byte[] out = outputBuffer.array();
        int length = out.length;
        while (out[length - 1] == 0)
            length--;

        byte[] result = new byte[length];
        System.arraycopy(out, 0, result, 0, length);

        // now return the converted bytes
        return result;
    }

    //--------------------------------------------------------------------------

    /**
     * Loads xml from a string and returns its root node 
       * (validates the xml if required).
     *
     * @param data 
     * @param validate
     * @return
     * @throws IOException
     * @throws JDOMException
     */
    public static Element loadString(String data, boolean validate) throws IOException, JDOMException {
        //SAXBuilder builder = new SAXBuilder(validate);
        SAXBuilder builder = getSAXBuilderWithoutXMLResolver(validate); // oasis catalogs are used
        Document jdoc = builder.build(new StringReader(data));

        return (Element) jdoc.getRootElement().detach();
    }

    //--------------------------------------------------------------------------

    /**
     * Loads xml from an input stream and returns its root node.
     *
     * @param input
     * @return
     * @throws IOException
     * @throws JDOMException
     */
    public static Element loadStream(InputStream input) throws IOException, JDOMException {
        SAXBuilder builder = getSAXBuilderWithoutXMLResolver(false); //new SAXBuilder();
        builder.setFeature("http://apache.org/xml/features/validation/schema", false);
        builder.setFeature("http://apache.org/xml/features/nonvalidating/load-external-dtd", false);
        builder.setExpandEntities(false);
        Document jdoc = builder.build(input);

        return (Element) jdoc.getRootElement().detach();
    }

    //--------------------------------------------------------------------------
    //---
    //--- Transform API
    //---
    //--------------------------------------------------------------------------

    /**
     * Transforms an xml tree into another using a stylesheet on disk.
     *
     * @param xml
     * @param styleSheetPath
     * @return
     * @throws Exception
     */
    public static Element transform(Element xml, String styleSheetPath) throws Exception {
        JDOMResult resXml = new JDOMResult();
        transform(xml, styleSheetPath, resXml, null);
        return (Element) resXml.getDocument().getRootElement().detach();
    }

    //--------------------------------------------------------------------------

    /**
     * Transforms an xml tree into another using a stylesheet on disk and pass parameters.
     *
     * @param xml
     * @param styleSheetPath
     * @param params
     * @return
     * @throws Exception
     */
    public static Element transform(Element xml, String styleSheetPath, Map<String, String> params)
            throws Exception {
        JDOMResult resXml = new JDOMResult();
        transform(xml, styleSheetPath, resXml, params);
        return (Element) resXml.getDocument().getRootElement().detach();
    }

    //--------------------------------------------------------------------------

    /**
     * Transforms an xml tree putting the result to a stream (uses a stylesheet on disk).
     *
     * @param xml
     * @param styleSheetPath
     * @param out
     * @throws Exception
     */
    public static void transform(Element xml, String styleSheetPath, OutputStream out) throws Exception {
        StreamResult resStream = new StreamResult(out);
        transform(xml, styleSheetPath, resStream, null);
    }

    //--------------------------------------------------------------------------

    /**
     * Transforms an xml tree putting the result to a stream  - no parameters.
     *
     * @param xml
     * @param styleSheetPath
     * @param result
     * @throws Exception
     */
    public static void transform(Element xml, String styleSheetPath, Result result) throws Exception {
        transform(xml, styleSheetPath, result, null);
    }

    //--------------------------------------------------------------------------

    private static class JeevesURIResolver implements URIResolver {

        /**
         *
         * @param href
         * @param base
         * @return
         * @throws TransformerException
         */
        public Source resolve(String href, String base) throws TransformerException {
            Resolver resolver = ResolverWrapper.getInstance();
            CatalogResolver catResolver = resolver.getCatalogResolver();
            if (Log.isDebugEnabled(Log.XML_RESOLVER)) {
                Log.debug(Log.XML_RESOLVER, "Trying to resolve " + href + ":" + base);
            }
            Source s = catResolver.resolve(href, base);
            // If resolver has a blank XSL file use it to replace 
            // resolved file that doesn't exist...
            String blankXSLFile = resolver.getBlankXSLFile();
            if (blankXSLFile != null && s.getSystemId().endsWith(".xsl")) {
                try {
                    if (Log.isDebugEnabled(Log.XML_RESOLVER)) {
                        Log.debug(Log.XML_RESOLVER, "  Check if exist " + s.getSystemId());
                    }
                    File f = URIUtil.toFile(new URI(s.getSystemId()));
                    if (Log.isDebugEnabled(Log.XML_RESOLVER))
                        Log.debug(Log.XML_RESOLVER, "Check on " + f.getPath() + " exists returned: " + f.exists());

                    // If the resolved resource does not exist, set it to blank file path to not trigger FileNotFound Exception
                    if (!(f.exists())) {
                        if (Log.isDebugEnabled(Log.XML_RESOLVER)) {
                            Log.debug(Log.XML_RESOLVER, "  Resolved resource " + s.getSystemId()
                                    + " does not exist. blankXSLFile returned instead.");
                        }
                        s.setSystemId(blankXSLFile);
                    }
                } catch (URISyntaxException e) {
                    Log.warning(Log.XML_RESOLVER, "URI syntax problem: " + e.getMessage());
                    e.printStackTrace();
                }
            }

            if (Log.isDebugEnabled(Log.XML_RESOLVER) && s != null) {
                Log.debug(Log.XML_RESOLVER, "Resolved as " + s.getSystemId());
            }
            return s;
        }
    }

    //--------------------------------------------------------------------------

    /**
     * Transforms an xml tree putting the result to a stream with optional parameters.
     *
     * @param xml
     * @param styleSheetPath
     * @param result
     * @param params
     * @throws Exception
     */
    public static void transform(Element xml, String styleSheetPath, Result result, Map<String, String> params)
            throws Exception {
        File styleSheet = new File(styleSheetPath);
        Source srcXml = new JDOMSource(new Document((Element) xml.detach()));
        Source srcSheet = new StreamSource(styleSheet);

        // Dear old saxon likes to yell loudly about each and every XSLT 1.0
        // stylesheet so switch it off but trap any exceptions because this
        // code is run on transformers other than saxon 
        TransformerFactory transFact = TransformerFactoryFactory.getTransformerFactory();
        transFact.setURIResolver(new JeevesURIResolver());
        try {
            transFact.setAttribute(FeatureKeys.VERSION_WARNING, false);
            transFact.setAttribute(FeatureKeys.LINE_NUMBERING, true);
            transFact.setAttribute(FeatureKeys.PRE_EVALUATE_DOC_FUNCTION, false);
            transFact.setAttribute(FeatureKeys.RECOVERY_POLICY, Configuration.RECOVER_SILENTLY);
            // Add the following to get timing info on xslt transformations
            //transFact.setAttribute(FeatureKeys.TIMING,true);
        } catch (IllegalArgumentException e) {
            Log.warning(Log.ENGINE, "WARNING: transformerfactory doesnt like saxon attributes!");
            //e.printStackTrace();
        } finally {
            Transformer t = transFact.newTransformer(srcSheet);
            if (params != null) {
                for (Map.Entry<String, String> param : params.entrySet()) {
                    t.setParameter(param.getKey(), param.getValue());
                }
            }
            t.transform(srcXml, result);
        }
    }

    //--------------------------------------------------------------------------

    /**
     * Clears the cache used in the stylesheet transformer factory. This will only work for the GeoNetwork Caching
     * stylesheet transformer factory. This is a no-op for other transformer factories.
     */
    public static void clearTransformerFactoryStylesheetCache() {
        TransformerFactory transFact = TransformerFactory.newInstance();
        try {
            Method cacheMethod = transFact.getClass().getDeclaredMethod("clearCache", null);
            cacheMethod.invoke(transFact, new Object[0]);
        } catch (Exception e) {
            Log.error(Log.ENGINE, "Failed to find/invoke clearCache method - continuing (" + e.getMessage() + ")");
        }

    }

    // --------------------------------------------------------------------------
    /**
    * Transform an xml tree to PDF using XSL-FOP 
    * putting the result to a stream (uses a stylesheet
    * on disk)
    */

    public static String transformFOP(String uploadDir, Element xml, String styleSheetPath) throws Exception {
        String file = uploadDir + UUID.randomUUID().toString() + ".pdf";

        // Step 1: Construct a FopFactory
        // (reuse if you plan to render multiple documents!)
        FopFactory fopFactory = FopFactory.newInstance();

        // Step 2: Set up output stream.
        // Note: Using BufferedOutputStream for performance reasons (helpful
        // with FileOutputStreams).
        OutputStream out = new BufferedOutputStream(new FileOutputStream(new File(file)));

        try {
            // Step 3: Construct fop with desired output format
            Fop fop = fopFactory.newFop(MimeConstants.MIME_PDF, out);

            // Step 4: Setup JAXP using identity transformer
            TransformerFactory factory = TransformerFactoryFactory.getTransformerFactory();
            factory.setURIResolver(new JeevesURIResolver());
            Source xslt = new StreamSource(new File(styleSheetPath));
            try {
                factory.setAttribute(FeatureKeys.VERSION_WARNING, false);
                factory.setAttribute(FeatureKeys.LINE_NUMBERING, true);
                factory.setAttribute(FeatureKeys.RECOVERY_POLICY, Configuration.RECOVER_SILENTLY);
            } catch (IllegalArgumentException e) {
                Log.warning(Log.ENGINE, "WARNING: transformerfactory doesnt like saxon attributes!");
                //e.printStackTrace();
            } finally {
                Transformer transformer = factory.newTransformer(xslt);

                // Step 5: Setup input and output for XSLT transformation
                // Setup input stream
                Source src = new JDOMSource(new Document((Element) xml.detach()));

                // Resulting SAX events (the generated FO) must be piped through to
                // FOP
                Result res = new SAXResult(fop.getDefaultHandler());

                // Step 6: Start XSLT transformation and FOP processing
                transformer.transform(src, res);
            }

        } finally {
            // Clean-up
            out.close();
        }

        return file;
    }

    //--------------------------------------------------------------------------
    //---
    //--- General stuff
    //---
    //--------------------------------------------------------------------------

    /**
     * Writes an xml element to a stream.
     *
     * @param doc
     * @param out
     * @throws IOException
     */
    public static void writeResponse(Document doc, OutputStream out) throws IOException {
        XMLOutputter outputter = new XMLOutputter(Format.getPrettyFormat());
        outputter.output(doc, out);
    }

    //---------------------------------------------------------------------------

    /**
     * Converts an xml element to a string.
     *
     * @param data
     * @return
     */
    public static String getString(Element data) {
        XMLOutputter outputter = new XMLOutputter(Format.getPrettyFormat());

        return outputter.outputString(data);
    }

    //---------------------------------------------------------------------------

    /**
     *
     * @param data
     * @return
     */
    public static String getString(DocType data) {
        XMLOutputter outputter = new XMLOutputter(Format.getPrettyFormat());

        return outputter.outputString(data);
    }

    //---------------------------------------------------------------------------

    /**
     *
     * @param data
     * @return
     */
    public static String getString(Document data) {
        XMLOutputter outputter = new XMLOutputter(Format.getPrettyFormat());

        return outputter.outputString(data);
    }

    //---------------------------------------------------------------------------

    /**
     * Creates and prepares an XPath element - simple xpath (like "a/b/c").
     *
     * @param xml
     * @param xpath
     * @param theNSs
     * @return
     * @throws JDOMException
     */
    private static XPath prepareXPath(Element xml, String xpath, List<Namespace> theNSs) throws JDOMException {
        XPath xp = XPath.newInstance(xpath);
        for (Namespace ns : theNSs) {
            xp.addNamespace(ns);
        }

        return xp;
    }

    //---------------------------------------------------------------------------

    /**
     * Retrieves a single XML element given a simple xpath (like "a/b/c").
     *
     * @param xml
     * @param xpath
     * @param theNSs
     * @return
     * @throws JDOMException
     */
    public static Object selectSingle(Element xml, String xpath, List<Namespace> theNSs) throws JDOMException {

        XPath xp = prepareXPath(xml, xpath, theNSs);

        return xp.selectSingleNode(xml);
    }

    //---------------------------------------------------------------------------

    /**
     * Retrieves a single XML element as a JDOM element given a simple xpath.
     *
     * @param xml
     * @param xpath
     * @return
     * @throws JDOMException
     */
    public static Element selectElement(Element xml, String xpath) throws JDOMException {
        return selectElement(xml, xpath, new ArrayList<Namespace>());
    }

    //---------------------------------------------------------------------------

    /**
     * Retrieves a single XML element as a JDOM element given a simple xpath.
     *
     * @param xml
     * @param xpath
     * @param theNSs
     * @return
     * @throws JDOMException
     */
    public static Element selectElement(Element xml, String xpath, List<Namespace> theNSs) throws JDOMException {
        Object result = selectSingle(xml, xpath, theNSs);
        if (result == null) {
            return null;
        } else if (result instanceof Element) {
            Element elem = (Element) result;
            return (Element) (elem);
        } else {
            //-- Found something but not an element
            return null;
        }
    }

    //---------------------------------------------------------------------------

    /**
     * Evaluates an XPath expression on an element and returns Elements.
     *
     * @param xml
     * @param xpath
     * @param theNSs
     * @return
     * @throws JDOMException
     */
    public static List<?> selectNodes(Element xml, String xpath, List<Namespace> theNSs) throws JDOMException {
        XPath xp = prepareXPath(xml, xpath, theNSs);
        return xp.selectNodes(xml);
    }

    /**
     * Evaluates an XPath expression on an document and returns Elements.
     *
     * @param xml
     * @param xpath
     * @param theNSs
     * @return
     * @throws JDOMException
     */
    public static List<?> selectDocumentNodes(Element xml, String xpath, List<Namespace> theNSs)
            throws JDOMException {
        XPath xp = XPath.newInstance(xpath);
        for (Namespace ns : theNSs) {
            xp.addNamespace(ns);
        }
        xml = (Element) xml.clone();
        Document document = new Document(xml);
        return xp.selectNodes(document);
    }

    //---------------------------------------------------------------------------

    /**
     * Evaluates an XPath expression on an element and returns Elements.
     * @param xml
     * @param xpath
     * @return
     * @throws JDOMException
     */
    public static List<?> selectNodes(Element xml, String xpath) throws JDOMException {
        return selectNodes(xml, xpath, new ArrayList<Namespace>());
    }

    //---------------------------------------------------------------------------

    /**
     * Evaluates an XPath expression on an element and returns string result.
     *
     * @param xml
     * @param xpath
     * @return
     * @throws JDOMException
     */
    public static String selectString(Element xml, String xpath) throws JDOMException {
        return selectString(xml, xpath, new ArrayList<Namespace>());
    }

    //---------------------------------------------------------------------------

    /**
     * Evaluates an XPath expression on an element and returns string result.
     *
     * @param xml
     * @param xpath
     * @param theNSs
     * @return
     * @throws JDOMException
     */
    public static String selectString(Element xml, String xpath, List<Namespace> theNSs) throws JDOMException {

        XPath xp = prepareXPath(xml, xpath, theNSs);

        return xp.valueOf(xml);
    }

    //---------------------------------------------------------------------------

    /**
     * Evaluates an XPath expression on an element and returns true/false.
     *
     * @param xml
     * @param xpath
     * @return
     * @throws JDOMException
     */
    public static boolean selectBoolean(Element xml, String xpath) throws JDOMException {
        String result = selectString(xml, xpath, new ArrayList<Namespace>());
        return result.length() > 0;
    }

    //---------------------------------------------------------------------------

    /**
     * Evaluates an XPath expression on an element and returns true/false.
     *
     * @param xml
     * @param xpath
     * @param theNSs
     * @return
     * @throws JDOMException
     */
    public static boolean selectBoolean(Element xml, String xpath, List<Namespace> theNSs) throws JDOMException {
        return selectString(xml, xpath, theNSs).length() > 0;
    }

    //---------------------------------------------------------------------------

    /**
     * Evaluates an XPath expression on an element and returns number result.
     *
     * @param xml
     * @param xpath
     * @return
     * @throws JDOMException
     */
    public static Number selectNumber(Element xml, String xpath) throws JDOMException {
        return selectNumber(xml, xpath, new ArrayList<Namespace>());
    }

    //---------------------------------------------------------------------------

    /**
     * Evaluates an XPath expression on an element and returns number result.
     *
     * @param xml
     * @param xpath
     * @param theNSs
     * @return
     * @throws JDOMException
     */
    public static Number selectNumber(Element xml, String xpath, List<Namespace> theNSs) throws JDOMException {

        XPath xp = prepareXPath(xml, xpath, theNSs);

        return xp.numberValueOf(xml);
    }

    //---------------------------------------------------------------------------

    /**
     * Error handler that collects up validation errors.
     *
     */
    public static class ErrorHandler extends DefaultHandler {

        private int errorCount = 0;
        private Element xpaths;
        private Namespace ns = Namespace.NO_NAMESPACE;
        private SAXOutputter so;

        public void setSo(SAXOutputter so) {
            this.so = so;
        }

        public boolean errors() {
            return errorCount > 0;
        }

        public Element getXPaths() {
            return xpaths;
        }

        public void addMessage(SAXParseException exception, String typeOfError) {
            if (errorCount == 0)
                xpaths = new Element("xsderrors", ns);
            errorCount++;

            Element elem = (Element) so.getLocator().getNode();
            Element x = new Element("xpath", ns);
            try {
                String xpath = jeeves.utils.XPath.getXPath(elem);
                //-- remove the first element to ensure XPath fits XML passed with
                //-- root element
                if (xpath.startsWith("/")) {
                    int ind = xpath.indexOf('/', 1);
                    if (ind != -1) {
                        xpath = xpath.substring(ind + 1);
                    } else {
                        xpath = "."; // error to be placed on the root element
                    }
                }
                x.setText(xpath);
            } catch (JDOMException e) {
                e.printStackTrace();
                x.setText("nopath");
            }
            String message = exception.getMessage() + " (Element: " + elem.getQualifiedName();
            String parentName;
            if (!elem.isRootElement()) {
                Element parent = (Element) elem.getParent();
                if (parent != null)
                    parentName = parent.getQualifiedName();
                else
                    parentName = "Unknown";
            } else {
                parentName = "/";
            }
            message += " with parent element: " + parentName + ")";

            Element m = new Element("message", ns).setText(message);
            Element errorType = new Element("typeOfError", ns).setText(typeOfError);
            Element errorNumber = new Element("errorNumber", ns).setText(String.valueOf(errorCount));
            Element e = new Element("error", ns);
            e.addContent(errorType);
            e.addContent(errorNumber);
            e.addContent(m);
            e.addContent(x);
            xpaths.addContent(e);
        }

        public void error(SAXParseException parseException) throws SAXException {
            addMessage(parseException, "ERROR");
        }

        public void fatalError(SAXParseException parseException) throws SAXException {
            addMessage(parseException, "FATAL ERROR");
        }

        public void warning(SAXParseException parseException) throws SAXException {
            addMessage(parseException, "WARNING");
        }

        /**
         * Set namespace to use for report elements
         * @param ns
         */
        public void setNs(Namespace ns) {
            this.ns = ns;
        }

        public Namespace getNs() {
            return ns;
        }
    }

    //---------------------------------------------------------------------------

    /**
     * Validates an XML document using the hints in the DocType (DTD validation) or schemaLocation attribute hint.
     *
     * @param doc
     * @throws Exception
     */
    public synchronized static void validate(Document doc) throws Exception {
        if (doc.getDocType() != null) { // assume DTD validation
            SAXBuilder builder = getSAXBuilder(true);
            Document document = builder.build(new StringReader(getString(doc)));
        }

        Element xml = doc.getRootElement();
        if (xml != null) { // try XSD validation
            String schemaLoc = xml.getAttributeValue("schemaLocation", xsiNS);
            if (schemaLoc == null || schemaLoc.equals("")) {
                throw new IllegalArgumentException(
                        "XML document missing/blank schemaLocation hints or DocType dtd - cannot validate");
            }
            validate(xml);
        } else {
            throw new IllegalArgumentException("XML document is missing root element - cannot validate");
        }
    }

    //---------------------------------------------------------------------------

    /**
     * Validates an XML document using the hints in the schemaLocation attribute.
     *
     * @param xml
     * @throws Exception
     */
    public synchronized static void validate(Element xml) throws Exception {
        Schema schema = factory().newSchema();
        ErrorHandler eh = new ErrorHandler();
        validateRealGuts(schema, xml, eh);
        if (eh.errors()) {
            Element xsdXPaths = eh.getXPaths();
            throw new XSDValidationErrorEx("XSD Validation error(s):\n" + getString(xsdXPaths), xsdXPaths);
        }
    }

    //---------------------------------------------------------------------------

    /**
     * Validates an xml document with respect to an xml schema described by .xsd file path.
     *
     * @param schemaPath
     * @param xml
     * @throws Exception
     */
    public static void validate(String schemaPath, Element xml) throws Exception {
        Element xsdXPaths = validateInfo(schemaPath, xml);
        if (xsdXPaths != null && xsdXPaths.getContent().size() > 0)
            throw new XSDValidationErrorEx("XSD Validation error(s):\n" + getString(xsdXPaths), xsdXPaths);
    }

    //---------------------------------------------------------------------------

    /**
     * Validates an xml document with respect to schemaLocation hints.
     *
     * @param xml
     * @return
     * @throws Exception
     */
    public static Element validateInfo(Element xml) throws Exception {
        ErrorHandler eh = new ErrorHandler();
        Schema schema = factory().newSchema();
        validateRealGuts(schema, xml, eh);
        if (eh.errors()) {
            return eh.getXPaths();
        } else {
            return null;
        }
    }

    //---------------------------------------------------------------------------

    /**
     * Validates an xml document with respect to schemaLocation hints using supplied error handler.
     *
     * @param xml
     * @param eh
     * @return
     * @throws Exception
     */
    public static Element validateInfo(Element xml, ErrorHandler eh) throws Exception {
        Schema schema = factory().newSchema();
        validateRealGuts(schema, xml, eh);
        if (eh.errors()) {
            return eh.getXPaths();
        } else {
            return null;
        }
    }

    //---------------------------------------------------------------------------

    /**
     * Validates an xml document with respect to an xml schema described by .xsd file path.
     *
     * @param schemaPath
     * @param xml
     * @return
     * @throws Exception
     */
    public static Element validateInfo(String schemaPath, Element xml) throws Exception {
        ErrorHandler eh = new ErrorHandler();
        validateGuts(schemaPath, xml, eh);
        if (eh.errors()) {
            return eh.getXPaths();
        } else {
            return null;
        }
    }

    //---------------------------------------------------------------------------

    /**
     * Validates an xml document with respect to an xml schema described by .xsd file path using supplied error handler.
     *
     * @param schemaPath
     * @param xml
     * @param eh
     * @return
     * @throws Exception
     */
    public static Element validateInfo(String schemaPath, Element xml, ErrorHandler eh) throws Exception {
        validateGuts(schemaPath, xml, eh);
        if (eh.errors()) {
            return eh.getXPaths();
        } else {
            return null;
        }
    }

    //---------------------------------------------------------------------------

    /**
     * Called by validation methods that supply an xml schema described by .xsd file path.
     *
     * @param schemaPath
     * @param xml
     * @param eh
     * @throws Exception
     */
    private static void validateGuts(String schemaPath, Element xml, ErrorHandler eh) throws Exception {
        StreamSource schemaFile = new StreamSource(new File(schemaPath));
        Schema schema = factory().newSchema(schemaFile);
        validateRealGuts(schema, xml, eh);
    }

    //---------------------------------------------------------------------------

    /**
     * Called by all validation methods to do the real guts of the validation job.
     * @param schema
     * @param xml
     * @param eh
     * @throws Exception
     */
    private static void validateRealGuts(Schema schema, Element xml, ErrorHandler eh) throws Exception {

        Resolver resolver = ResolverWrapper.getInstance();

        ValidatorHandler vh = schema.newValidatorHandler();
        vh.setResourceResolver(resolver.getXmlResolver());
        vh.setErrorHandler(eh);

        SAXOutputter so = new SAXOutputter(vh);
        eh.setSo(so);

        so.output(xml);
    }

    private static SchemaFactory factory() {
        return SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
    }

    //---------------------------------------------------------------------------

    /**
      * Converts an xml element to JSON
      * 
      * @param xml the XML element
      * @return the JSON response
      * 
      * @throws IOException
      */
    public static String getJSON(Element xml) throws IOException {
        return Xml.getJSON(Xml.getString(xml));
    }

    /**
     * Converts an xml string to JSON
     * 
     * @param xml the XML element
     * @return the JSON response
     * 
     * @throws IOException
     */
    public static String getJSON(String xml) throws IOException {
        XMLSerializer xmlSerializer = new XMLSerializer();

        // Disable type hints. When enable, a type attribute in the root 
        // element will throw NPE.
        // http://sourceforge.net/mailarchive/message.php?msg_id=27646519
        xmlSerializer.setTypeHintsEnabled(false);
        xmlSerializer.setTypeHintsCompatibility(false);
        JSON json = xmlSerializer.read(xml);
        return json.toString(2);
    }

}