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 ...).

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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));

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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.