On Jun 16, 6:16 am, Kieran Topping <[EMAIL PROTECTED]> wrote:
> I thought I would document some recent experience I've have, trying to
> get E4X to work.
> Thankfully my efforts ended in success, but I did encounter a few
> jar-dependency & xml-parser issues, which took a while to fix - in
> particular because googling the exception messages didn't yield much
> information. Hopefully this post might address this and save someone
> else a bit of time!
>
> The results below were generated by running the attached java class
> (E4X.java) from the command line, on a 1.5 JVM. The java class runs a
> very simple javascript script which generates a small xml fragment and
> outputs it to the screen.
> The expected output is:
> <y>a & b</y>
>
> 1. My first attempt to run this was using Rhino-1.6R7.
> [kieran]$ env CLASSPATH=./js-1.6R7.jar:$CLASSPATH java E4X
> Exception in thread "main" org.mozilla.javascript.EcmaError: TypeError:
> error: Unexpected character encountered (lex state 3): 'b' (<cmd>#3)
> ...
>
> I haven't actually worked out what is causing this problem, but I think
> that it was a bug in the xmlbeans library (which Rhino-1.6R7 uses). In
> any case, I moved on as follows:
>
> 2. I then tried Rhino-1.7R1
> [kieran]$ env CLASSPATH=./js-1.7R1.jar:$CLASSPATH java E4X
> Exception in thread "main" java.lang.UnsupportedOperationException:
> This DocumentBuilder, "org.apache.xerces.jaxp.DocumentBuilderImpl", does
> not support the reset functionality. Specification "null" version "null"
> ...
>
> This problem seems to be caused by the my Xerces version not being
> sufficiently up to date.
> I haven't tried all versions, but what I /can/ say is that 2.0.1 & 2.6.2
> both generate this exception.
>
> 3. So, I installed the most recent xerces library
> [kieran]$ env CLASSPATH=./js-1.7R1.jar:./xercesImpl-2.9.0.jar:$CLASSPATH
> java E4X
> <parent/>
>
> This was the weirdest problem that I encountered. Whatever the contents
> of my javascript XML object, "<parent/>" was the only output that was
> ever generated!
>
> 4. As I suspected that some other jar was interfering somehow, I
> systematically removed jars from my CLASSPATH, and re-tested. It turned
> out that as soon as I removed saxon-6.5.4.jar from my CLASSPATH, the
> java worked as expected:
>
> [kieran]$ NOSAXONCLASSPATH=$(echo $CLASSPATH | perl -np -e
> 's/saxon-6.5.4.jar//')
> [kieran]$ env
> CLASSPATH=./js-1.7R1.jar:./xercesImpl-2.9.0.jar:$NOSAXONCLASSPATH java E4X
> <y>a & b</y>
>
> So, I had got Rhino/E4X to work as required by:
> 1. Upgrading to Rhino1.7R1.
> 2. Upgrading to Xerces 2.9.0.
> 3. Uninstalling Saxon 6.5.4.
>
> However, Saxon 6.5.4 is an is integral part of our application (hey, it
> works fine for us, and upgrading would be very non-trivial), so I had to
> find a solution that didn't involve uninstalling Saxon.
>
> Saxon uses the "Services API" to inform
> javax.xml.transform.TransformerFactory which TransformerFactory
> implementation it should return when the static newInstance() method is
> called. Saxon tells it to use "com.icl.saxon.TransformerFactoryImpl".
>
> For some reason (probably too difficult/time-consuming to investigate)
> the Rhino/E4X library doesn't interact correctly with transformers
> generated by the Saxon factory: "com.icl.saxon.TransformerFactoryImpl".
>
> If you're interested, my "solution" was to amend the Saxon jar such that
> it doesn't specify which TransformerFactory to use (by deleting the
> files in META-INF/services); the bits of my application that need a
> "com.icl.saxon.TransformerFactoryImpl", I've explicitly amended to
> request one.
>
> I hope this helps someone!
>
> Kieran
>
> [E4X.java]import org.mozilla.javascript.*;
>
> public class E4X {
> public static void main(String args[])
> throws Exception
> {
> Context cx = Context.enter();
> try {
> Scriptable scope = cx.initStandardObjects();
> Object result = cx.evaluateString(
> scope,
> "var x = <example>a & b</example>; \n"+
> "var y = <y/>; \n"+
> "y.appendChild(x.text()); \n"+
> "y.toXMLString(); ",
> "<cmd>", 1, null
> );
> System.out.println(Context.toString(result));
> } finally {
> Context.exit();
> }
> }
>
> }
Bizarre-- the E4X implementation in Rhino 1.7R1 just uses the XML
parser from javax.xml. Your example program worked just fine for me
with only the Rhino jar in the classpath.
--N
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