source: main/trunk/greenstone3/src/java/org/greenstone/gsdl3/util/XMLTransformer.java@ 26457

/*
 *    XMLTransformer.java
 *    Copyright (C) 2002 New Zealand Digital Library, http://www.nzdl.org
 *
 *    This program is free software; you can redistribute it and/or modify
 *    it under the terms of the GNU General Public License as published by
 *    the Free Software Foundation; either version 2 of the License, or
 *    (at your option) any later version.
 *
 *    This program 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 General Public License for more details.
 *
 *    You should have received a copy of the GNU General Public License
 *    along with this program; if not, write to the Free Software
 *    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */
package org.greenstone.gsdl3.util;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileWriter;
import java.io.InputStreamReader;
import java.io.StringReader;
import java.io.StringWriter;
import java.io.UnsupportedEncodingException;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;

import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.transform.ErrorListener;
import javax.xml.transform.Source;
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.apache.log4j.Logger;
import org.greenstone.util.GlobalProperties;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;

/**
 * XMLTransformer - utility class for greenstone
 * 
 * transforms xml using xslt
 * 
 * @author Katherine Don
 * @version $Revision: 26457 $
 */
public class XMLTransformer
{
    private static int debugFileCount = 0; // for unique filenames when debugging XML transformations with physical files

    static Logger logger = Logger.getLogger(org.greenstone.gsdl3.util.XMLTransformer.class.getName());

    /** The transformer factory we're using */
    TransformerFactory t_factory = null;

    /**
     * The no-arguments constructor.
     * 
     * Any exceptions thrown are caught internally
     * 
     * @see javax.xml.transform.TransformerFactory
     */
    public XMLTransformer()
    {
        // http://download.oracle.com/docs/cd/E17476_01/javase/1.5.0/docs/api/index.html?javax/xml/transform/TransformerFactory.html states that
        // TransformerFactory.newInstance() looks in jar files for a Factory specified in META-INF/services/javax.xml.transform.TransformerFactory, 
        // else it will use the "platform default"
        // In this case: xalan.jar's META-INF/services/javax.xml.transform.TransformerFactory contains org.apache.xalan.processor.TransformerFactoryImpl
        // as required.

        // This means we no longer have to do a System.setProperty("javax.xml.transform.TransformerFactory", "org.apache.xalan.processor.TransformerFactoryImpl");
        // followed by a this.t_factory = org.apache.xalan.processor.TransformerFactoryImpl.newInstance();
        // The System.setProperty step to force the TransformerFactory implementation that gets used, conflicts with
        // Fedora (visiting the Greenstone server pages breaks the Greenstone-tomcat hosted Fedora pages) as Fedora 
        // does not include the xalan.jar and therefore can't then find the xalan TransformerFactory explicitly set.

        // Gone back to forcing use of xalan transformer, since other jars like crimson.jar, which may be on some
        // classpaths, could be be chosen as the TransformerFactory implementation over xalan. This is what used to
        // give problems before. Instead, have placed copies of the jars that Fedora needs (xalan.jar and serializer.jar 
        // and the related xsltc.jar which it may need) into packages/tomcat/lib so that it's on the server's classpath
        // and will be found by Fedora.

        // make sure we are using the xalan transformer
        System.setProperty("javax.xml.transform.TransformerFactory", "org.apache.xalan.processor.TransformerFactoryImpl");
        try
        {
            this.t_factory = org.apache.xalan.processor.TransformerFactoryImpl.newInstance();
            //this.t_factory = TransformerFactory.newInstance();
            this.t_factory.setErrorListener(new TransformErrorListener()); // handle errors in the xml Source used to instantiate transformers
        }
        catch (Exception e)
        {
            logger.error("exception creating t_factory " + e.getMessage());
        }
    }

    /**
     * Transform an XML document using a XSLT stylesheet
     * 
     * @param stylesheet
     *            a filename for an XSLT stylesheet
     * @param xml_in
     *            the XML to be transformed
     * @return the transformed XML
     */
    public String transform(String stylesheet, String xml_in)
    {

        try
        {
            TransformErrorListener transformerErrorListener = (TransformErrorListener) this.t_factory.getErrorListener();
            transformerErrorListener.setStylesheet(stylesheet);
            // Use the TransformerFactory to process the stylesheet Source and generate a Transformer.
            Transformer transformer = this.t_factory.newTransformer(new StreamSource(stylesheet));

            // Use the Transformer to transform an XML Source and send the output to a Result object.
            StringWriter output = new StringWriter();
            StreamSource streamSource = new StreamSource(new StringReader(xml_in));
            transformer.setErrorListener(new TransformErrorListener(stylesheet, streamSource));
            transformer.transform(streamSource, new StreamResult(output));
            return output.toString();
        }
        catch (TransformerConfigurationException e)
        {
            logger.error("couldn't create transformer object: " + e.getMessageAndLocation());
            logger.error(e.getLocationAsString());
            return "";
        }
        catch (TransformerException e)
        {
            logger.error("couldn't transform the source: " + e.getMessageAndLocation());
            return "";
        }
    }

    public String transformToString(Document stylesheet, Document source)
    {
        return transformToString(stylesheet, source, null);
    }

    public String transformToString(Document stylesheet, Document source, HashMap parameters)
    {

        try
        {
            TransformErrorListener transformerErrorListener = (TransformErrorListener) this.t_factory.getErrorListener();
            transformerErrorListener.setStylesheet(stylesheet);
            // Use the TransformerFactory to process the stylesheet Source and generate a Transformer.
            Transformer transformer = this.t_factory.newTransformer(new DOMSource(stylesheet));
            if (parameters != null)
            {
                Set params = parameters.entrySet();
                Iterator i = params.iterator();
                while (i.hasNext())
                {
                    Map.Entry m = (Map.Entry) i.next();
                    transformer.setParameter((String) m.getKey(), m.getValue());
                }
            }
            //transformer.setParameter("page_lang", source.getDocumentElement().getAttribute(GSXML.LANG_ATT));

            // Use the Transformer to transform an XML Source and send the output to a Result object.
            StringWriter output = new StringWriter();
            DOMSource domSource = new DOMSource(source);

            transformer.setErrorListener(new TransformErrorListener(stylesheet, domSource));
            transformer.transform(domSource, new StreamResult(output));
            return output.toString();
        }
        catch (TransformerConfigurationException e)
        {
            logger.error("couldn't create transformer object: " + e.getMessageAndLocation());
            logger.error(e.getLocationAsString());
            return "";
        }
        catch (TransformerException e)
        {
            logger.error("couldn't transform the source: " + e.getMessageAndLocation());
            return "";
        }
    }

    /**
     * Transform an XML document using a XSLT stylesheet, but using a DOMResult
     * whose node should be set to the Document donated by resultNode
     */
    public Node transform_withResultNode(Document stylesheet, Document source, Document resultNode)
    {
        return transform(stylesheet, source, null, null, resultNode);
    }

    public Node transform(Document stylesheet, Document source)
    {
        return transform(stylesheet, source, null, null, null);
    }

    public Node transform(Document stylesheet, Document source, HashMap<String, Comparable> parameters)
    {
        return transform(stylesheet, source, parameters, null, null);
    }

    public Node transform(Document stylesheet, Document source, HashMap<String, Comparable> parameters, Document docDocType)
    {
        return transform(stylesheet, source, parameters, docDocType, null);
    }

    protected Node transform(Document stylesheet, Document source, HashMap<String, Comparable> parameters, Document docDocType, Document resultNode)
    {
        try
        {
            // Use the TransformerFactory to process the stylesheet Source and generate a Transformer.
            TransformErrorListener transformerErrorListener = (TransformErrorListener) this.t_factory.getErrorListener();
            transformerErrorListener.setStylesheet(stylesheet);
            Transformer transformer = this.t_factory.newTransformer(new DOMSource(stylesheet));
            //logger.info("XMLTransformer transformer is " + transformer); //done in ErrorListener

            if (parameters != null)
            {
                Set params = parameters.entrySet();
                Iterator i = params.iterator();
                while (i.hasNext())
                {
                    Map.Entry m = (Map.Entry) i.next();
                    transformer.setParameter((String) m.getKey(), m.getValue());
                }
            }

            // When we transform the DOMResult, we need to make sure the result of
            // the transformation has a DocType. For that to happen, we need to create
            // the DOMResult using a Document with a predefined docType.
            // If we don't have a DocType then do the transformation with a DOMResult
            // that does not contain any doctype (like we use to do before).
            DOMResult result = docDocType == null ? new DOMResult() : new DOMResult(docDocType);
            if (resultNode != null)
            {
                result.setNode(resultNode);
            }
            DOMSource domSource = new DOMSource(source);
            transformer.setErrorListener(new TransformErrorListener(stylesheet, domSource));
            transformer.transform(domSource, result);
            return result.getNode(); // pass the entire document
        }
        catch (TransformerConfigurationException e)
        {
            return transformError("XMLTransformer.transform(Doc, Doc, HashMap, Doc)" + "\ncouldn't create transformer object", e);
        }
        catch (TransformerException e)
        {
            return transformError("XMLTransformer.transform(Doc, Doc, HashMap, Doc)" + "\ncouldn't transform the source", e);
        }
    }

    public Node transform(File stylesheet, File source)
    {
        return transform(stylesheet, source, null);
    }

    // debugAsFile is only to be set to true when either the stylesheet or source parameters 
    // are not objects of type File. The debugAsFile variable is passed into the 
    // TransformErrorListener. When set to true, the TransformErrorListener will itself create
    // two files containing the stylesheet and source XML, and try to transform the new source
    // file with the stylesheet file for debugging purposes.
    protected Node transform(File stylesheet, File source, Document docDocType)
    {
        try
        {
            TransformErrorListener transformerErrorListener = (TransformErrorListener) this.t_factory.getErrorListener();
            transformerErrorListener.setStylesheet(stylesheet);
            Transformer transformer = this.t_factory.newTransformer(new StreamSource(new InputStreamReader(new FileInputStream(stylesheet), "UTF-8")));
            DOMResult result = (docDocType == null) ? new DOMResult() : new DOMResult(docDocType);
            StreamSource streamSource = new StreamSource(new InputStreamReader(new FileInputStream(source), "UTF-8"));

            transformer.setErrorListener(new TransformErrorListener(stylesheet, streamSource));

            transformer.transform(streamSource, result);
            return result.getNode().getFirstChild();
        }
        catch (TransformerConfigurationException e)
        {
            return transformError("XMLTransformer.transform(File, File)" + "\ncouldn't create transformer object for files\n" + stylesheet + "\n" + source, e);
        }
        catch (TransformerException e)
        {
            return transformError("XMLTransformer.transform(File, File)" + "\ncouldn't transform the source for files\n" + stylesheet + "\n" + source, e);
        }
        catch (UnsupportedEncodingException e)
        {
            return transformError("XMLTransformer.transform(File, File)" + "\ncouldn't read file due to an unsupported encoding\n" + stylesheet + "\n" + source, e);
        }
        catch (FileNotFoundException e)
        {
            return transformError("XMLTransformer.transform(File, File)" + "\ncouldn't find the file specified\n" + stylesheet + "\n" + source, e);
        }
    }

    // Given a heading string on the sort of transformation error that occurred and the exception object itself, 
    // this method prints the exception to the tomcat window (system.err) and the greenstone log and then returns
    // an xhtml error page that is constructed from it.
    protected Node transformError(String heading, Exception e)
    {
        String message = heading + "\n" + e.getMessage();
        logger.error(heading + ": " + e.getMessage());

        if (e instanceof TransformerException)
        {
            String location = ((TransformerException) e).getLocationAsString();
            if (location != null)
            {
                logger.error(location);
                message = message + "\n" + location;
            }
        }
        System.err.println("****\n" + message + "\n****");
        return constructErrorXHTMLPage(message);
    }

    // Given an error message, splits it into separate lines based on any newlines present and generates an xhtml page
    // (xml Element)  with paragraphs for each line. This is then returned so that it can be displayed in the browser.
    public static Element constructErrorXHTMLPage(String message)
    {
        try
        {
            String[] lines = message.split("\n");

            Document xhtmlDoc = DocumentBuilderFactory.newInstance().newDocumentBuilder().newDocument();
            // <html></html>
            Node htmlNode = xhtmlDoc.createElement("html");
            xhtmlDoc.appendChild(htmlNode);
            // <head></head>
            Node headNode = xhtmlDoc.createElement("head");
            htmlNode.appendChild(headNode);
            // <title></title>
            Node titleNode = xhtmlDoc.createElement("title");
            headNode.appendChild(titleNode);
            Node titleString = xhtmlDoc.createTextNode("Error occurred");
            titleNode.appendChild(titleString);

            // <body></body>
            Node bodyNode = xhtmlDoc.createElement("body");
            htmlNode.appendChild(bodyNode);

            // finally put the message in the body
            Node h1Node = xhtmlDoc.createElement("h1");
            bodyNode.appendChild(h1Node);
            Node headingString = xhtmlDoc.createTextNode("The following error occurred:");
            h1Node.appendChild(headingString);

            //Node textNode = xhtmlDoc.createTextNode(message);
            //bodyNode.appendChild(textNode);

            for (int i = 0; i < lines.length; i++)
            {
                Node pNode = xhtmlDoc.createElement("p");
                Node textNode = xhtmlDoc.createTextNode(lines[i]);
                pNode.appendChild(textNode);
                bodyNode.appendChild(pNode);
            }

            return xhtmlDoc.getDocumentElement();

        }
        catch (Exception e)
        {
            String errmsg = "Exception trying to construct error xhtml page from message: " + message + "\n" + e.getMessage();
            System.err.println(errmsg);
            logger.error(errmsg);
            return null;
        }
    }

    // ErrorListener class for both Transformer objects and TransformerFactory objects.
    // This class can be used to register a handler for any fatal errors, errors and warnings that
    // may occur when either transforming an xml file with an xslt stylesheet using the XMLTransformer,
    // or when instantiating a Transformer object using the XMLTransformer's TransformerFactory member var.
    // The latter case occurs when the xml Source used to instantiate a Transformer from a TransformerFactory
    // is invalid in some manner, which results in a null Transformer object. However, as no 
    // TransformerConfigurationException or TransformerException are thrown in this case, the errors 
    // would have not been noticed until things go wrong later when trying to use the (null) Transformer.
    //
    // The errors caught by this ErrorListener class are printed both to the greenstone.log and to the 
    // tomcat console (System.err), and the error message is stored in the errorMessage variable so that 
    // it can be retrieved and be used to generate an xhtml error page.
    public class TransformErrorListener implements ErrorListener
    {
        protected String errorMessage = null;
        protected String stylesheet = null;
        protected Source source = null; // can be DOMSource or StreamSource
        protected boolean debugAsFile = true; // true if xslt or source are not real physical files

        // *********** METHODS TO BE CALLED WHEN SETTING AN ERROR LISTENER ON TRANSFORMERFACTORY OBJECTS
        // The default constructor is only for when setting an ErrorListener on TransformerFactory objects
        public TransformErrorListener()
        {
            this.stylesheet = null;
            this.source = null;
            XMLTransformer.debugFileCount++;
        }

        public void setStylesheet(Document xslt)
        {
            this.debugAsFile = true;
            this.stylesheet = GSXML.elementToString(xslt.getDocumentElement(), true);
            this.source = null;
        }

        public void setStylesheet(String xslt)
        {
            this.debugAsFile = true;
            this.stylesheet = xslt;
            this.source = null;
        }

        public void setStylesheet(File xslt)
        {
            this.debugAsFile = false; // if this constructor is called, we're dealing with physical files for both xslt and source          
            this.stylesheet = xslt.getAbsolutePath();
            this.source = null;
        }

        // *********** METHODS TO BE CALLED WHEN SETTING AN ERROR LISTENER ON TRANSFORMERFACTORY OBJECTS
        // When setting an ErrorListener on Transformer object, the ErrorListener takes a Stylesheet xslt and a Source      
        public TransformErrorListener(String xslt, Source source)
        {
            this.stylesheet = xslt;
            this.source = source;
            XMLTransformer.debugFileCount++;
        }

        public TransformErrorListener(Document xslt, Source source)
        {
            this.stylesheet = GSXML.elementToString(xslt.getDocumentElement(), true);
            this.source = source;
            XMLTransformer.debugFileCount++;
        }

        public TransformErrorListener(File xslt, Source source)
        {
            this.debugAsFile = false; // if this constructor is called, we're dealing with physical files for both xslt and source
            this.source = source;
            this.stylesheet = xslt.getAbsolutePath(); // not necessary to get the string from the file
            // all we were going to do with it *on error* was write it out to a file anyway     
        }

        // *********** METHODS CALLED AUTOMATICALLY ON ERROR

        //  Receive notification of a recoverable error.
        public void error(TransformerException exception)
        {
            handleError("Error:\n", exception);
        }

        // Receive notification of a non-recoverable error.
        public void fatalError(TransformerException exception)
        {
            handleError("Fatal Error:\n", exception);
        }

        // Receive notification of a warning.
        public void warning(TransformerException exception)
        {
            handleError("Warning:\n", exception);
        }

        public String toString(TransformerException e)
        {
            String msg = "Exception encountered was:\n\t";
            String location = e.getLocationAsString();
            if (location != null)
            {
                msg = msg + "Location: " + location + "\n\t";
            }

            return msg + "Message: " + e.getMessage();
        }

        // clears the errorPage variable after the first call to this method
        public String getErrorMessage()
        {
            String errMsg = this.errorMessage;
            if (this.errorMessage != null)
            {
                this.errorMessage = null;
            }
            return errMsg;
        }

        // sets the errorMessage member variable to the data stored in the exception
        // and writes the errorMessage to the logger and tomcat's System.err
        protected void handleError(String errorType, TransformerException exception)
        {

            this.errorMessage = errorType + toString(exception);

            // If either the stylesheet or the source to be transformed with it were not files,
            // so that the transformation was performed in-memory, then the "location" information
            // during the error handling (if any) wouldn't have been helpful.
            // To allow proper debugging, we write both stylesheet and source out as physical files
            // and perform the same transformation again, so that when a transformation error does 
            // occur, the files are not in-memory but can be viewed, and any location information
            // for the error given by the ErrorListener will be sensible (instead of the unhelpful
            // "line#0 column#0 in file://somewhere/dummy.xsl").
            // Note that if the stylesheet and the source it is to transform were both physical 
            // files to start off with, we will not need to perform the same transformation again
            // since the error reporting would have provided accurate locations for those.
            if (debugAsFile)
            {

                performTransformWithPhysicalFiles(); // will give accurate line numbers

                // No need to print out the current error message (seen in the Else statement below), 
                // as the recursive call to XMLTransformer.transform(File, File, false) in method
                // performTransformWithPhysicalFiles() will do this for us.
            }
            else
            {
                // printing out the error message
                // since !debugAsFile, we are dealing with physical files, 
                // variable stylesheet would have stored the filename instead of contents
                this.errorMessage = this.errorMessage + "\nstylesheet filename: " + stylesheet;

                this.errorMessage += "\nException CAUSE:\n" + exception.getCause();
                System.err.println("\n****Error transforming xml:\n" + this.errorMessage + "\n****\n");
                //System.err.println("Stylesheet was:\n + this.stylesheet + "************END STYLESHEET***********\n\n");           

                logger.error(this.errorMessage);

                // now print out the source to a file, and run the stylesheet on it using a transform()
                // then any error will be referring to one of these two input files.
            }
        }

        // This method will redo the transformation that went wrong with *real* files: 
        // it writes out the stylesheet and source XML to files first, then performs the transformation
        // to get the actual line location of where things went wrong (instead of "line#0 column#0 in dummy.xsl")
        protected void performTransformWithPhysicalFiles()
        {
            File webLogsTmpFolder = new File(GlobalProperties.getGSDL3Home() + File.separator + "logs" + File.separator + "tmp");
            if (!webLogsTmpFolder.exists())
            {
                webLogsTmpFolder.mkdirs(); // create any necessary folders
            }
            File styleFile = new File(webLogsTmpFolder + File.separator + "stylesheet" + XMLTransformer.debugFileCount + ".xml");
            File sourceFile = new File(webLogsTmpFolder + File.separator + "source" + XMLTransformer.debugFileCount + ".xml");
            try
            {
                // write stylesheet to a file called stylesheet_systemID in tmp
                FileWriter styleSheetWriter = new FileWriter(styleFile);
                styleSheetWriter.write(stylesheet, 0, stylesheet.length());
                styleSheetWriter.flush();
                styleSheetWriter.close();
            }
            catch (Exception e)
            {
                System.err.println("*** Exception when trying to write out stylesheet to " + styleFile.getAbsolutePath());
            }

            if (this.source != null)
            { // ErrorListener was set on a Transformer object
                try
                {
                    FileWriter srcWriter = new FileWriter(sourceFile);
                    String contents = "";
                    if (source instanceof DOMSource)
                    {
                        DOMSource domSource = (DOMSource) source;
                        Document doc = (Document) domSource.getNode();
                        contents = GSXML.elementToString(doc.getDocumentElement(), true);
                        //contents = GSXML.xmlNodeToXMLString(domSource.getNode());
                    }
                    else if (source instanceof StreamSource)
                    {
                        StreamSource streamSource = (StreamSource) source;
                        BufferedReader reader = new BufferedReader(streamSource.getReader());
                        String line = "";
                        while ((line = reader.readLine()) != null)
                        {
                            contents = contents + line + "\n";
                        }
                    }
                    srcWriter.write(contents, 0, contents.length());
                    srcWriter.flush();
                    srcWriter.close();
                }
                catch (Exception e)
                {
                    System.err.println("*** Exception when trying to write out stylesheet to " + sourceFile.getAbsolutePath());
                }
            }

            System.err.println("*****************************************");
            System.err.println("Look for stylesheet in: " + styleFile.getAbsolutePath());
            if (this.source != null)
            { // ErrorListener was set on a Transformer object
                System.err.println("Look for source XML in: " + sourceFile.getAbsolutePath());
            }

            // now perform the transform again, which will assign another TransformErrorListener
            // but since debuggingAsFile is turned off, we won't recurse into this section of
            // handling the error again
            if (this.source != null)
            { // ErrorListener was set on a Transformer object
                XMLTransformer.this.transform(styleFile, sourceFile); // calls the File, File version, so debugAsFile will be false     
            }
            else
            { // ErrorListener was set on a TransformerFactory object

                // The recursive step in this case is to perform the instantiation 
                // of the Transformer object again.
                // Only one TransformerFactory object per XMLTransformer, 
                // and only one TransformerHandler object set on any TransformerFactory
                // But the stylesheet used to create a Transformer from that TransformerFactory
                // object changes each time, by calls to setStylesheet(), 
                // Therefore, the debugAsFile state for the single TransformerFactory's 
                // TransformerHandler changes each time also.

                try
                {
                    debugAsFile = false;
                    this.stylesheet = styleFile.getAbsolutePath();
                    //TransformErrorListener transformerErrorListener = (TransformErrorListener)XMLTransformer.this.t_factory.getErrorListener();
                    //transformerErrorListener.setStylesheet(styleFile);
                    Transformer transformer = XMLTransformer.this.t_factory.newTransformer(new StreamSource(styleFile));
                    if (transformer == null)
                    {
                        String msg = "XMLTransformer transformer is " + transformer;
                        logger.info(msg);
                        System.out.println(msg + "\n****\n");
                    }
                }
                catch (TransformerConfigurationException e)
                {
                    String message = "Couldn't create transformer object: " + e.getMessageAndLocation();
                    logger.error(message);
                    logger.error(e.getLocationAsString());
                    System.out.println(message);
                }
            }
        }
    }
}