trireme-xslt

This module presents an abstraction of XLST processing. It is specifically designed for the Trireme platform to allow efficient processing of XSLT when Node.js applications are run on Java.

Basically, when this module is running on Trireme, it uses the XSLT processor provided by the Java platform. When it is not, it uses the "node_xslt" module, which in turn uses libxslt.

Trireme is an implementation of Node.js on top of the Java virtual machine. It makes it possible to embed Node.js into applications where it would be more difficult to go currently, and gives direct access to native Java technologies from Node.js.

One technology that is particularly mature on Java is XML processing, and this module provides that access.

One advantage of this module is that it can use features of the Java language that allow the processing to take place in a thread pool, making it possible to take advantage of extra CPU cores for XSLT processing -- which can be CPU-intensive and is highly parallelizable. This happens automatically in Trireme when a callback is passed to the "transform" function.

In order to make it possible to test apps outside Trireme, this module will detect if it is running in Trireme and if not it will use the "node_xslt" module instead.

This module requires Trireme 0.7.4 or higher. For more on Trireme, check it out on GitHub:

https://github.com/apigee/trireme

Example

var fs = require('fs');
var xslt = require('trireme-xslt');

var stylesheetText = fs.readFileSync('../fixtures/samplestylesheet.xsl');
var cs = xslt.compileStylesheet(stylesheetText);

var input = '<Hello>This is some XML!</Hello>';

// Synchronous transformation
var result = xslt.transform(cs, input);

// Async transformation
xslt.transform(cs, input, function(err, result) {
  console.log('The result of the transformation is %s', result);
});

// Transformation with parameters
xslt.transform(cs, input, 
  { foo: 'foo', bar: 123 },
  function(err, result) {
    console.log('The result of the transformation is %s', result);
});

Functions

compileStylesheet(stylesheet)

Parses the specified XSLT stylesheet for future processing. "stylesheet" must be a string or a Buffer.

Compiling a stylesheet is an expensive operation. For best results, compile it once when the application is started, and re-use it for multiple transformations.

transform(compiledStylesheet, document, parameters, callback)

Transforms the XML based on the stylesheet. The stylesheet must previously have been compiled using "compileStylesheet."

If specified, "parameters" must be an object. Each property in the object will be passed as a parameter to the XSLT engine, so that it may be retrieved usign the "xsl:param" tag.

If "callback" is specified and a function, then the processing may proceed asynchronously. The result will be delivered via the callback. The first argument will be an Error if processing fails, and undefined otherwise. The second will be a string that represents the output of the transformation.

setTransformer(transformerClass)

Specifies which Java class to use for XSLT transformation.

Trireme Operation

When using this module on Trireme, XSLT processing is handled by the platform's "TransformerFactory." A different transformer may be specified by calling "setTransformer". If a callback is used, then "transform" runs the XSLT in a thread pool, so it can take advantage of multiple CPU cores.

Within Trireme, the number of concurrent XSLT processing jobs is limited to 8 in order to avoid blowing up the thread pool in extreme situations. This default may be adjusted by setting the Java system property "trireme.max.xslt.jobs".

Local Operation

When using this module outside Trireme, all features are implemented using the "node_xslt" module, which under the covers uses "libxslt." Outside Trireme, all transformations are performed synchronously.