converting XML with XSLT

[Bron Czimes]

hey there,

i'm trying to convert an XML document with XSLT and all I'm getting is a blank page (no error msg's or anything).
my code is

// Java core packages
import java.io.*;
import java.util.*;
 
//Java extension packages
import javax.servlet.*;
import javax.servlet.http.*;
import javax.xml.parsers.*;
import javax.xml.transform.*;
import javax.xml.transform.dom.*;
import javax.xml.transform.stream.*;
 
// third party packages
import org.w3c.dom.*;
import org.xml.sax.*;
 
/**
 *
 * @author  bron
 * @version
 */
public class viewFlight extends HttpServlet {
    
    protected void doGet(HttpServletRequest request,
    HttpServletResponse response) throws ServletException, IOException
    
    {
        try{
        HttpSession thisSession = request.getSession(false);
        
        // RequestDispatcher to forward client to home page if no
        // no session exists or no flights are selected
        RequestDispatcher dispatcher = request.getRequestDispatcher("index.jsp");
        
        // If session does not exist, forward to index.jsp
        if (thisSession == null){
            dispatcher.forward(request, response);
        }
        
        // Get flights from session objects
        List flights = (List) thisSession.getAttribute("flights");
        
        // Locate FlightBean object for selected flight
        Iterator iter = flights.iterator();
        FlightBean flight = null;
        
        String flightNum = request.getParameter("FlightNbr");
   
        while(iter.hasNext()){
            flight = (FlightBean) iter.next();
            
            if(flightNum.equals(flight.getFlightNbr())){
                // Save the flight in session attribute
                thisSession.setAttribute("flightToAdd", flight);
                break; //flightNum matches current flight
            }
        }
        // If flight is not in the list, forward to index.jsp
        if(flight == null)
            dispatcher.forward(request, response);
 
        
        // Get XML document and transform for browser client
            // Get a DocumentBuilderFactory for creating a DocumentBuilder
            DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
            
            // Get a DocumentBuilder for building the DOM tree
            DocumentBuilder builder = factory.newDocumentBuilder();
            
            // Create a new Document(empty DOM tree)
            Document messageDocument = builder.newDocument();
            
            //get XML from FlightBean and append to Document
            Element flightElement = flight.getXML(messageDocument);
            messageDocument.appendChild(flightElement);
            
            response.setContentType("text/html");
            PrintWriter out = response.getWriter();
            
            // Open InputStream for XSL document
            InputStream xslStream = getServletContext().getResourceAsStream("/styleeffect.xsl");
            
            // Transform XML document using XSLT
            transform(messageDocument, xslStream, out);
            
            // flush and close PrintWriter
            out.flush();
            out.close();
        }
        // catch XML parser exceptions
        catch(ParserConfigurationException pcException ){
            pcException.printStackTrace();
        }
    }
    // Transform XML Document using provided XSLT InputStream
    // and write resulting document to provided PrintWriter
    private void transform(Document document, InputStream xslStream, PrintWriter output) {
        try{
            // create DOMSource for source XML document
            Source xmlSource = new DOMSource(document);
            
            // create StreamSource for XSLT document
            Source xslSource = new StreamSource(xslStream);
            
            // create StreamResult for transformation result
            Result result = new StreamResult(output);
            
            // create TransformerFactory to obtain a Transformer
            TransformerFactory transformerFactory = TransformerFactory.newInstance();
            
            // create Transformer for performing XSL transformation
            Transformer transformer = transformerFactory.newTransformer(xslSource);
                       
            // perform transformation and deliver content to client
            transformer.transform(xmlSource, result);
        }
        // handle exception when transforming XML document
        catch(TransformerException transformerException){
            transformerException.printStackTrace(System.err);
        }
    } //end of transform
       
}//end of viewFlight servlet

sorry, I don't know much about the conversion process for XSLT. am i doing something wrong here?

Ta

[Balan Raj]

Bron,
I dont see you using the "RESULT" of the transformation.

The process is something like

//transform
transformer.transform(xmlSource, streamResult);
//convert to bYteArray
 byte[] ba = byteArrayOutputStream.toByteArray();
//Create string
 String baString = new String(ba, "UTF-8");
//print string
out.println(baString);
 
  

In your case, I dont see "out" being set at all..

[Bron Czimes]

sorry, i don't think i understand. my XSLT actually creates a web page (sorry, i didn't include my XSLT code before).
so as far as I was aware i'm unable to use out in this context.

my XSLT code is this

<?xml version="1.0" encoding="UTF-8" ?>
 
<!--
    Document   : styleeffect.xsl
    Created on : 17 September 2004, 15:17
    Author     : bron
    Description:
        Purpose of transformation follows.
-->
 
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
    <xsl :-o	 utput method = "xml" omit-xml-declaration = "no" 
   indent = "yes" doctype-system = 
   "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"
   doctype-public = "-//W3C//DTD XHTML 1.0 Strict//EN"/>
 
    <!-- TODO customize transformation rules 
         syntax recommendation <a href="http://www.w3.org/TR/xslt" target="_blank" rel="nofollow">http://www.w3.org/TR/xslt</a> 
    -->
    <xsl:template match="flight">
        <html xmlns = "http://www.w3.org/1999/xhtml">
            <head>
                <title></title>
                <center><h2><description><xsl:value-of select = "departureCity"/></description>
                </h2></center>
                <link rel = "stylesheet" href = "../styles.css" type = "text/css" />
            </head>
            <body bgcolor="cornflowerblue">
            
             <center><table>
                <tr>
 
                <!-- create table cells -->
                <td class = "label">Flight Nbr:</td>
 
                <td><xsl:value-of select = "flightNbr"/></td>
                </tr>
                <td class = "label">Departure City:</td>
 
                <td><xsl:value-of select = "departureCity"/></td>
                </tr>
                <tr>
 
                <td class = "label">Destination City:</td>
 
                <td><xsl:value-of select = "destination"/></td>
                </tr>
                <tr>
 
                <td class = "label">Flight Type:</td>
 
                <td><xsl:value-of select = "flightType"/></td>
                </tr>
                <tr>
 
                <td class = "label">Flight Date:</td>
 
                <td><xsl:value-of select = "flightDate"/></td>
                </tr>
                <tr>
 
                <td class = "label">Departure Time:</td>
 
                <td><xsl:value-of select = "departTime"/></td>
                </tr>
                <tr>
 
                <td class = "label">Arrival Time:</td>
 
                <td><xsl:value-of select = "arrivalTime"/></td>
                </tr>
                <tr>
 
                <td class = "label">Price:</td>
 
                <td><xsl:value-of select = "cost"/></td>
                </tr>
                
                <tr>
 
                 <!-- create Booking button -->
                    <td>
                        <form method = "post" action = "bookFlight"><p>
                            <input type = "submit" value = "Book Flight" />
                            </p></form>
                    </td>
 
                 <!-- create View Bookings button in row 5 -->
                    <td>
                        <form method = "get" action = "viewBookings.jsp"><p>
                            <input type = "submit" value = "View Bookings" />
                            </p></form>
                    </td>
                </tr>
                </table></center>
 
            
            </body>
        </html>
    </xsl:template>
 
</xsl:stylesheet>
 

does that help any more?

[Bron Czimes]

btw, i know that I am missing a <tr> tag near the top there, but I have fixed that and I still have the same problem....

[Sheldon Fernandes]

Check the content of the xml (messageDocument) used in the transformation.

// Create a new Document(empty DOM tree)
Document messageDocument = builder.newDocument();

//get XML from FlightBean and append to Document
Element flightElement = flight.getXML(messageDocument);
messageDocument.appendChild(flightElement);

If it is correct, try doing the transformation from the command line using the xsl and an xml file.

My xsl is a bit rusty, shouldn't the template contain a forward slash? I could be wrong here.
<xsl:template match="/flight">
[EDIT: As I had suspected, I got this one wrong]


Sheldon Fernandes
[ September 28, 2004: Message edited by: Sheldon Fernandes ]

[Jeroen Wenting]

Working code to do what you want is the following:

protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException
{
String contentType = null;
Document doc = null;
String xsl = null;

contentType = (String)request.getAttribute("contenttype");
if (contentType == null) contentType = defContentType;
doc = (Document)request.getAttribute("xml-doc");
xsl = (String)request.getAttribute("xsl-file-name");
String path = getServletContext().getRealPath("/WEB-INF/xsl/");
// Output goes in the response stream.
PrintWriter out = response.getWriter();

if (doc == null || xsl == null)
{
String errorMsg = "";
if (doc == null)
errorMsg += "XML document missing from call to OutputGenerator<br />";
if (xsl == null)
errorMsg += "XSL filename missing from call to OutputGenerator<br />";
StringBuffer buf = generateError(errorMsg);
log(errorMsg);
out.write(buf.toString());
return;
}

// The servlet returns HTML.
response.setContentType(contentType);    
if (cache == null) cache = new HashMap();
Transformer t = null;
// Get the XML input document and the stylesheet.
Source xmlSource = new DOMSource(doc);
// Perform the transformation, sending the output to the response.

// XSL processing can be time consuming, but this is mainly due to the overhead
// of compiling the XSL sheet. 
// By caching the compiled sheets, the process is speeded up dramatically.
// Time saved on subsequent requests can be 99% or more (hundreds of milliseconds).
try
{
// check if the XSL sheet was found in cache, and use that if available
if (cache.containsKey(xsl)) t = (Transformer)cache.get(xsl);
else
{
// otherwise, load the XSL sheet from disk, compile it and store the compiled
// sheet in the cache
TransformerFactory tFactory = TransformerFactory.newInstance();
Source xslSource = new StreamSource(new File(path, xsl+".xsl"));
t = tFactory.newTransformer(xslSource);
cache.put(xsl, t);
}
// perform the XSL transformation of the XML Document into the servlet outputstream
t.transform(xmlSource, new StreamResult(out));
}
catch (TransformerConfigurationException e)
{
e.printStackTrace();
throw new ServletException(e);
}
catch (TransformerFactoryConfigurationError e)
{
e.printStackTrace();
throw new ServletException(e);
}
catch (TransformerException e)
{
e.printStackTrace();
throw new ServletException(e);
}
 
}

generateError() is just a method that takes a String and parses that into an HTML template to generate a custom error page.
The XML to be processed and the NAME of the XSL file are passed in as request parameters.
The servlet caches the precompiled XSL sheets in order to speed up performance on subsequent uses of the same XSL (depending on your parser this can make requests after the first one for a particular XSL file up to a hundred times faster according to tests I did).

[Sheldon Fernandes]

Hi Bron,

I tried testing your xsl (in xmlspy) using the following xml file.

<?xml version="1.0" encoding="UTF-8"?>
<flight>
<departureCity>Mumbai</departureCity>
<flightNbr>CD10213</flightNbr>
<destination>Tokyo</destination>
<flightType>Business</flightType>
<flightDate>30/12/1213</flightDate>
<departTime>10:00</departTime>
<arrivalTime>3:00</arrivalTime>
<cost>4.34</cost>
</flight>

I ran the transformation as is and it gave me an empty page.
It worked when I put a value in <title></title> element. Check the markup in the head section.

Sheldon Fernandes

[Bron Czimes]

hi Sheldon,
thankyou for going to so much trouble to work it out. that made it work for me too. i didn't realise that a title was a mandatory item.
thankyou, thankyou, thankyou!!

Bron

[Mark Spritzler]

Good Topic, but unfortunately off topic for the Servlets forum. This would be better asked in the XML and related product forum.

Since the question has already been answered correctly, I am just going to close this thread.

Mark