Note: This tip uses JAXP. The classes are also part of the Java 2 SDK 1.4, so if you have 1.4 installed, you don't need any additional software. (See Resources for the Xalan-J transformation engine.)

Using TrAX

To perform a transformation using TrAX, you need to define the source, result, and XSL stylesheet, then create a Transformer and use it to actually perform the transformation. You can view the coding for this in Listing 1.

In this case, you create the Source and Result using the StreamSource and StreamResult objects, which take as their arguments the URI for files.

In order to use SAX as input or output, you need to change the way you create the Source and Result.

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A SAX stream as the Source object

Now that you have the basic foundation, let's look at using a SAX stream as the input for the transformation:

                

...
import javax.xml.transform.sax.SAXSource;

import org.xml.sax.helpers.XMLReaderFactory;
import org.xml.sax.XMLReader;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;

public class TransformSAX extends Object {
  public static void main (String args[]) throws Exception
  {
    try {
       String XMLFileName = "mySource.xml";
       String OutputFileName = "myResult.xml";
       String StyleFileName = "myStyle.xsl";
         
       String parserClass = 
          "org.apache.crimson.parser.XMLReaderImpl";
       XMLReader reader = 
          XMLReaderFactory.createXMLReader(parserClass);
       Source source = 
          new SAXSource(reader, new InputSource(XMLFileName));

       Result result = new StreamResult(OutputFileName);
       Source style = new StreamSource(StyleFileName);

       TransformerFactory transFactory = 
       TransformerFactory.newInstance();
       Transformer trans = transFactory.newTransformer(style);

       trans.transform(source, result);
         
    } catch (SAXException e) {
        System.out.println(e.getMessage());
    }         

  }
}

Notice that everything stays the same except the creation of the Source object. The purpose of the XMLReader object in any SAX application is to generate events based on the document's content and send them to another application. In most cases, that application is a ContentHandler object. But in this case, the XMLReader sends its events to the Transformer through the SAXSource object that's created with it as a foundation.

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A SAX stream as the Result object

Usually, SAX and XSL transformations interact because the input for a SAX application is data that is being manipulated through XSLT before processing by the SAX ContentHandler. To accomplish this, you need to create a transformation that outputs to the SAX stream.

Actually, you're not really outputting to a SAX stream, but replacing it. In a normal SAX application, the XMLReader produces events, such as startElement or endDocument, that are consumed by the ContentHandler object. When you use a SAXResult in a transformation, what you're really doing is replacing the XMLReader and feeding events directly to a ContentHandler:

                

...
import javax.xml.transform.sax.SAXResult;
import org.xml.sax.ContentHandler;

public class TransformSAX extends Object {
  public static void main (String args[]) throws Exception
  {
    try {
       String XMLFileName = "mySource.xml";
       String StyleFileName = "myStyle.xsl";
         
       String parserClass = 
             "org.apache.crimson.parser.XMLReaderImpl";
       XMLReader reader = 
             XMLReaderFactory.createXMLReader(parserClass);
       Source source = 
             new SAXSource(reader, new InputSource(XMLFileName));

         ContentHandler theHandler = new MyHandler();
         Result result = new SAXResult(theHandler);
                  
       Source style = new StreamSource(StyleFileName);

       TransformerFactory transFactory = 
             TransformerFactory.newInstance();
       Transformer trans = transFactory.newTransformer(style);

       trans.transform(source, result);
         
    } catch (SAXException e) {
        System.out.println(e.getMessage());
    }         

  }
}

Here, as before, everything stays the same except for the creation of the Result object -- and the ultimate results. The SAXResult takes the ContentHandler object of your choice as the argument, and when the Transformer actually performs the transformation, that's where the results go, and not to the original file. Notice that you don't even have the results file defined any more.

Instead, the theHandler object receives the events as though they'd come from an XMLReader directly, and acts on them just as it would in a traditional SAX application.

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Summary

This tip demonstrates a simple application that both consumes and produces a stream of SAX events, allowing you to integrate XSL transformations into your applications directly, without the hassle of having to create intermediate files or other objects to hold your data.

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Download

Information about download methods

Resources

• Download the source files for this tip.
  
  
• If you want to download the Xalan-J transformation engine separately, you can find it at http://xml.apache.org.
  
  
• Get more information on the Simple API for XML (SAX).
  
  
• Read the developerWorks Understanding SAX tutorial (developerWorks, September 2001).
  
  
• Read the developerWorks Transforming XML documents tutorial (developerWorks, May 2000).
  
  
• Find more XML resources on the developerWorks XML zone.
  
  
• IBM trial software: Build your next development project with trial software available for download directly from developerWorks.
  
  
• Find out how you can become an IBM Certified Developer in XML and related technologies.
  
  
• Want us to send you useful XML tips like this every week? Sign up for the developerWorks XML Tips newsletter.
  
  

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Table of contents

• Using TrAX
• SAX stream as Source object
• SAX stream as Result object
• Summary
• Download
• Resources
• About the author
• Comments

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