XSLT Chain improvement [INT-675]

[spring-operator]

Sebastien Chatel opened INT-675 and commented

Allows chained XSL Transformations, and minimize memory footprint by using a SAX filter chain.

It can be achieve with a javax.xml.transform.sax.TransformerHandler.

We can extend this to all other XML Transformations (XPath, XQuery, custom XMLFilter, FOP ...).

---

Affects: 1.0.2

Reference URL: http://forum.springsource.org/showthread.php?s=4f72efe116e8721864c3080448ab4c4c&p=246666

Attachments:

• xslt-chained-poc.zip (5.62 kB)

[spring-operator]

Sebastien Chatel commented

To understand how to build a SAX filter chain.

The chain looks like this :

SAXResult1 => TransformerHandler1 => SAXResult2 => TransformerHandler2 => Result3

Here is how to build such a chain in a general manner :

// final result
Result result3 = new StreamResult(out);

// second transformer
TransformerHandler handler2 = factory.newTransformerHandler(templates2);
// connect it to the final result
handler2.setResult(result3);

// first transformer ...
TransformerHandler handler1 = factory.newTransformerHandler(templates1);
// connect it to second transformer ...
handler1.setResult(new SAXResult(handler2));

// transform
factory.newTransformer().transform(source, new SAXResult(handler1));

---

DelayedResult object implements the "chain of responsability" pattern :

DelayedResult.write( streamResult )
/* connect handler2 to streamResult, then */
/* Result result2 = new SAXResult(handler2) */
DelayedResult.write( result2 )
/* connect handler1 to result2, then */
/* Result result1 = new SAXResult(handler1) */
Delayed.write( result1 )
/* transform source to result1*/

[spring-operator]

Jonas Partner commented

Thanks for that Sebastien, would you be interested in submitting this as a patch with tests?

[spring-operator]

Sebastien Chatel commented

Hello Jonas,

I would be interested, but for the moment, i'm working on a more complete use of SAX. Not only for XSLT.

After reading this article "Implement complicated data transformations with SAX and XSLT"
http://www.javaworld.com/javaworld/jw-09-2005/jw-0905-xslt.html?page=5

i had some ideas, what do you think of this :

------8<--------8<---------8<-------------
<chain>

<!--!-- something before -->

<sax:transform-chain>
    <sax:producer />
    <sax:filter ref="myFilter" />
    <sax:xsl-transformer xsl-resource="classpath:/file1.xsl" />
    <sax:xsl-transformer xsl-resource="classpath:/file2.xsl" />
    <sax:serializer to="string" />
</sax:transform-chain>

<!-- something after -->

</chain>
------8<--------8<---------8<-------------

Producer and Serializer elements are always required. I thing the SAX model is correctly formalized this way.
Producer transforms any payload to a SAX Stream. When the payload in not in xml format (txt, csv, or any entreprise proprietary format), you can provide your own implementation : <sax:producer ref="myCustomProducer" />

Filters are standard XMLFilterImpl.

Serializer, serializes the SAX Stream into a result type : DOM, JDom, Dom4j, String, byte[], ... and for experimental, a DelayedResult.