fop/src/org/apache/fop/apps/XSLTInputHandler.java

/* 
 * Copyright (C) 2001 The Apache Software Foundation. All rights reserved.
 * For details on use and redistribution please refer to the 
 * LICENSE file included with these sources."
 */


package org.apache.fop.apps;


// Imported TraX classes
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.stream.StreamSource;
import javax.xml.transform.sax.SAXResult;
import javax.xml.transform.sax.SAXSource;
import javax.xml.transform.sax.SAXTransformerFactory;

// Imported SAX classes
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
import org.xml.sax.XMLReader;
import org.xml.sax.XMLFilter;


// Imported java.io classes
import java.io.InputStream;
import java.io.IOException;
import java.io.File;

// FOP
import org.apache.fop.messaging.MessageHandler;

/**
 * XSLTInputHandler basically takes an xmlfile and transforms it with an xsltfile
 * and the resulting xsl:fo document is input for Fop.
 */

public class XSLTInputHandler extends InputHandler {

	File xmlfile, xsltfile;

    public XSLTInputHandler (File xmlfile, File xsltfile ) {
        this.xmlfile = xmlfile;
		this.xsltfile = xsltfile;
    }

    /**
      *  overwrites the method of the super class to return the xmlfile
      */
    public InputSource getInputSource () {
        return fileInputSource(xmlfile);
    }

    /**
      *  overwrites this method of the super class and returns an XMLFilter instead of a
      *  simple XMLReader which allows chaining of transformations
      *
      */
    public XMLReader getParser() {
        return this.getXMLFilter(xmlfile,xsltfile);
    }

    /**
      * Creates from the transformer an instance of an XMLFilter which
      * then can be used in a chain with the XMLReader passed to Driver. This way
      * during the conversion of the xml file + xslt stylesheet the resulting
      * data is fed into Fop. This should help to avoid memory problems
      * @param xmlfile The xmlfile containing the text data
      * @param xsltfile An xslt stylesheet
      * @return XMLFilter an XMLFilter which can be chained together with other XMLReaders or XMLFilters
      */
    private XMLFilter getXMLFilter (File xmlfile, File xsltfile) {
        try {
            // Instantiate  a TransformerFactory.
            TransformerFactory tFactory = TransformerFactory.newInstance();
            // Determine whether the TransformerFactory supports The use uf SAXSource
            // and SAXResult
            if (tFactory.getFeature(SAXSource.FEATURE) &&
                    tFactory.getFeature(SAXResult.FEATURE)) {
                // Cast the TransformerFactory to SAXTransformerFactory.
                SAXTransformerFactory saxTFactory =
                  ((SAXTransformerFactory) tFactory);
                // Create an XMLFilter for each stylesheet.
                XMLFilter xmlfilter = saxTFactory.newXMLFilter(
                                        new StreamSource(xsltfile));

                // Create an XMLReader.
                XMLReader parser = super.createParser();
                if (parser == null) {
                    MessageHandler.errorln("ERROR: Unable to create SAX parser");
                    System.exit(1);
                }

                // xmlFilter1 uses the XMLReader as its reader.
                xmlfilter.setParent(parser);
                return xmlfilter;
            } else {
                MessageHandler.errorln(
                  "Your parser doesn't support the features SAXSource and SAXResult." +
                  "\nMake sure you are using a xsl parser which supports TrAX");
                System.exit(1);
                return null;
            }
        }
        catch (Exception ex) {
            MessageHandler.errorln(ex.toString());
            return null;
        }
    }
}