It's Alive!http://norman.walsh.name/2006/04/21/xprocRuns9452006-04-21T16:13:06-04:00$Date: 2007-04-05 09:55:02 -0400 (Thu, 05 Apr 2007) $NormanWalsh2006Norman WalshMy XProc implementation successfully loaded and evaluated it's
first pipeline without throwing an exception, hanging, or otherwise falling
over. Pardon the melodramatic title, please.T. S.EliotSuccess is relative; it is what we make of the
mess we have made of things.I'm determined to build an implementation of
XProc as
we develop it,
so for the past couple of weeks I've been carving out as much time as
I can to get some sort of a skeleton off the ground. It's too early in
the process to imagine that I'm implementing the language that
our
specification will eventually describe, but I'm shooting in the
right direction, I hope.In broad strokes, my implementation strategy is to
represent each step in the pipeline as a component that can run
in its own thread. Bolt the inputs to the outputs, unleash the threads,
throw StAX
events through the pipes, wait until done, and then pick up the
output. I'm sure it'll grow more complicated than that, but for a very
simple pipeline, that works.Yesterday, my code ran it's first pipeline, constructed by
hand something like this:…
Load loadStyle = new Load();
loadStyle.setParam ("href", new DocumentReader("/projects/src/StaxTest/test/style.xsl"));
Load loadDoc = new Load();
loadDoc.setParam ("href", new DocumentReader("/projects/src/StaxTest/test/input.xml"));
XSLT10 transform = new XSLT10();
Connector styleConn = new Connector();
Connector docConn = new Connector();
loadStyle.setOutput ("output", styleConn.getWriter());
transform.setInput ("stylesheet", styleConn.getReader());
loadDoc.setOutput ("output", docConn.getWriter ());
transform.setInput ("document", docConn.getReader ());
…Today, it loaded and evaluated a pipeline document
describing that pipeline:<p:pipeline xmlns:p="http://xproc.org/ns/p">
<p:step name="p:xslt10">
<p:input name="document" label="doc"/>
<p:input name="stylesheet" label="style"/>
<p:output name="output" label="out"/>
</p:step>
<p:step name="p:load">
<p:param name="href" value="/projects/src/StaxTest/test/style.xsl"/>
<p:output name="output" label="style"/>
</p:step>
<p:step name="p:load">
<p:param name="href" value="/projects/src/StaxTest/test/input.xml"/>
<p:output name="output" label="doc"/>
</p:step>
<p:step name="p:save">
<p:param name="href" value="/tmp/pipeout.xml"/>
<p:input name="input" label="out"/>
</p:step>
</p:pipeline>Sweet! (Yes, it's silly to put the XSLT step before
the load steps, but I was testing the code that picks a component order.)It loads a configuration file to determine how to initialize
each component (e.g., what class to
instantiate). The configuration file also tells it something about the
inputs, outputs, and parameters (e.g., the
fact that href on the “load” component
identifies an input file that has to be parsed, but
href on the “save” component is just a string).
Baby steps, sure, but it put a smile on my face to see:run:
Node: 1: p:load: 1
Node: 2: p:load: 2
Node: 3: p:xslt10: 3
Node: 4: p:save: 4
INFO: Set param href (tree)
INFO: Set output output
INFO: Set input stylesheet
INFO: Set param href (tree)
INFO: Set output output
INFO: Set input document
INFO: Set output output
INFO: Set input input
INFO: Set param href=/tmp/pipeout.xml
Starting component for p:load
Starting component for p:load
INFO: Running Load
INFO: Running Load
Starting component for p:xslt10
Starting component for p:save
INFO: Running XSLT10
INFO: Running Save.
INFO: Skipping bogus attempt to write some sort of namespace decl attribute
BUILD SUCCESSFUL (total time: 0 seconds)I'm gonna call that a days work.
Time for a drink, I think!