source: main/trunk/greenstone3/src/java/org/greenstone/gsdl3/util/XMLTransformer.java@ 25613

/*
 *    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 org.greenstone.util.GlobalProperties;

// XML classes
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.TransformerConfigurationException;
import javax.xml.transform.TransformerException;
import javax.xml.transform.ErrorListener;

import javax.xml.transform.stream.StreamSource;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.Source;
import javax.xml.transform.stream.StreamResult;
import javax.xml.transform.dom.DOMResult;

import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.DocumentBuilder;
import org.w3c.dom.Element;
import org.w3c.dom.Document;

import org.w3c.dom.Node;
import org.w3c.dom.NodeList;

// other java classes
import java.io.StringReader;
import java.io.StringWriter;
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.File;
import java.util.HashMap;
import java.util.Set;
import java.util.Map;
import java.util.Iterator;

import org.apache.xml.utils.DefaultErrorHandler;

import org.apache.log4j.*;

/** XMLTransformer - utility class for greenstone
 *
 * transforms xml using xslt
 *
 * @author <a href="mailto:[email protected]">Katherine Don</a>
 * @version $Revision: 25613 $
 */
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 parameters) {
        return transform(stylesheet, source, parameters, null, null);
    }

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

    protected Node transform(Document stylesheet, Document source, HashMap 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(stylesheet));
        DOMResult result = (docDocType == null) ? new DOMResult() : new DOMResult(docDocType);
        StreamSource streamSource = new StreamSource(source);

        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);
    }   
    }
     
    // 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, TransformerException e) {
        String message = heading + "\n" + e.getMessage();
        logger.error(heading + ": " + e.getMessage());
        
        String location = 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);
            }
            catch (TransformerException e)
            {
                String message = "Couldn't transform the source: " + e.getMessageAndLocation();
                logger.error(message);
                System.out.println(message);
            }
        }
        
        }
    }
}