RESTFUL GlassFish XML XSLT stylesheet Java transformation produces EMPTY output

Question

I am writing a RESTFUL web service in Java. The idea is to "cut down" an XML document and strip away all the un-needed content (~98%) and leave only the tags we're interested in, while maintaining the document's structure, which is as follows (I cannot provide the actual XML content for confidentiality reasons):

<sear:SEGMENTS xmlns="http://www.exlibrisgroup.com/xsd/primo/primo_nm_bib" xmlns:sear="http://www.exlibrisgroup.com/xsd/jaguar/search">
   <sear:JAGROOT>
      <sear:RESULT>
         <sear:DOCSET IS_LOCAL="true" TOTAL_TIME="176" LASTHIT="9" FIRSTHIT="0" TOTALHITS="262" HIT_TIME="11">
            <sear:DOC SEARCH_ENGINE_TYPE="Local Search Engine" SEARCH_ENGINE="Local Search Engine" NO="1" RANK="0.086826384" ID="2347460">
               [
               <PrimoNMBib>
                  <record>
                     <display>
                        <title></title>
                     </display>
                     <sort>
                        <author></author>
                     </sort>
                  </record>
               </PrimoNMBib>
               ]
            </sear:DOC>
         </sear:DOCSET>
      </sear:RESULT>
   </sear:JAGROOT>
</sear:SEGMENTS>

Of course, this is the structure of only the tags we are interested in - there are hundreds more tags, but they are irrelevant.

The square brackets ([]) are not part of the XML and indicate that the element are elements of a list of children and occur more than once - one per match of the search from the RESTFUL service.

This being said, my Java code containing the XSLT stylesheet is as follows:

    import java.io.StringReader;
    import java.io.StringWriter;

    import javax.xml.transform.Transformer;
    import javax.xml.transform.TransformerException;
    import javax.xml.transform.TransformerFactory;
    import javax.xml.transform.TransformerFactoryConfigurationError;
    import javax.xml.transform.stream.StreamResult;
    import javax.xml.transform.stream.StreamSource;

    public String cutXML() throws TransformerFactoryConfigurationError, TransformerException
    {

       String xmlSourceResource = this.xml; // where this.xml is the full XML string of structure as presented above

       String xsltResource =
       "<xsl:stylesheet version=\"1.0\" xmlns:xsl=\"http://www.w3.org/1999/XSL/Transform\" xmlns:sear=\"http://www.exlibrisgroup.com/xsd/jaguar/search\">" +

       "    <xsl:output method=\"xml\" version=\"1.0\" omit-xml-declaration=\"no\" encoding=\"UTF-8\" indent=\"yes\"/>" +
       "    <xsl:strip-space elements=\"*\"/>" +

       "    <sear:WhiteList>" +
       "        <name>title</name>" +
       "        <name>author</name>" +                
       "    </sear:WhiteList>" +

       "    <xsl:template match=\"node()|@*\">" +
       "        <xsl:copy>" +
       "            <xsl:apply-templates select=\"node()|@*\"/>" +
       "        </xsl:copy>" +
       "    </xsl:template>" +

       "    <xsl:template match=\"*[not(descendant-or-self::*[name()=document('')/*/sear:WhiteList/*])]\"/>" +

       "</xsl:stylesheet>";

       StringWriter xmlResultResource = new StringWriter(); // where the transformed/stripped-down XML will be written

       Transformer xmlTransformer = TransformerFactory.newInstance().newTransformer(new StreamSource(new StringReader(xsltResource))); // create transformer object with XSLT given

       xmlTransformer.transform(new StreamSource(new StringReader(xmlSourceResource)), new StreamResult(xmlResultResource)); // transform XML with transformer and write into result StringWriter

       return xmlResultResource.getBuffer().toString(); // return transformed XML string

    }

Unfortunately, when I run it on the server, all I get is an empty page with an empty source, as if the result of the transformation was an empty String.

The server's log file first gave the following information:

    [#|2012-04-26T18:26:24.967+0000|INFO|glassfish3.1.2|com.sun.jersey.api.core.PackagesResourceConfig|_ThreadID=23;_ThreadName=Thread-2;|Scanning for root resource and provider classes in the packages: dk.kb.mobileservice|#]

    [#|2012-04-26T18:26:24.969+0000|INFO|glassfish3.1.2|com.sun.jersey.api.core.ScanningResourceConfig|_ThreadID=23;_ThreadName=Thread-2;|Root resource classes found: class dk.kb.mobileservice.Middle|#]

    [#|2012-04-26T18:26:24.970+0000|INFO|glassfish3.1.2|com.sun.jersey.api.core.ScanningResourceConfig|_ThreadID=23;_ThreadName=Thread-2;|No provider classes found.|#]

    [#|2012-04-26T18:26:24.978+0000|INFO|glassfish3.1.2|com.sun.jersey.server.impl.application.WebApplicationImpl|_ThreadID=23;_ThreadName=Thread-2;|Initiating Jersey application, version 'Jersey: 1.11 12/09/2011 10:27 AM'|#]

    [#|2012-04-26T18:26:25.192+0000|INFO|glassfish3.1.2|javax.enterprise.system.container.web.com.sun.enterprise.web|_ThreadID=23;_ThreadName=Thread-2;|WEB0671: Loading application [kb2] at [/kb2]|#]

    [#|2012-04-26T18:26:25.200+0000|INFO|glassfish3.1.2|javax.enterprise.system.tools.admin.org.glassfish.deployment.admin|_ThreadID=23;_ThreadName=Thread-2;|kb2 was successfully deployed in 2,293 milliseconds.|#]

    [#|2012-04-26T18:26:46.263+0000|SEVERE|glassfish3.1.2|javax.enterprise.system.std.com.sun.enterprise.server.logging|_ThreadID=20;_ThreadName=Thread-2;|SystemId Unknown; Line #0; Column #0; java.lang.NullPointerException |#]

    [#|2012-04-26T18:31:09.772+0000|SEVERE|glassfish3.1.2|javax.enterprise.system.std.com.sun.enterprise.server.logging|_ThreadID=21;_ThreadName=Thread-2;|SystemId Unknown; Line #0; Column #0; java.lang.NullPointerException |#]

and now it returns the following issues:

    [#|2012-04-27T00:05:07.731+0000|SEVERE|glassfish3.1.2|javax.enterprise.system.std.com.sun.enterprise.server.logging|_ThreadID=21;_ThreadName=Thread-2;|Error on line 1 column 1 of file:/root/webglassfish3/glassfish/domains/domain1/config/: SXXP0003: Error reported by XML parser: Content is not allowed in prolog.|#]

    [#|2012-04-27T00:05:07.732+0000|SEVERE|glassfish3.1.2|javax.enterprise.system.std.com.sun.enterprise.server.logging|_ThreadID=21;_ThreadName=Thread-2;|Recoverable error on line 1 SXXP0003: org.xml.sax.SAXParseException: Content is not allowed in prolog.|#]

I've tested the XML file and transformed it via browser, and it worked, so I don't think it's the XML's nor the XSLT stylesheet's fault... It seems to be a Java issue.

When I run the above Java code on the entire XML outside of GlassFish, I get the following errors:

    Exception in thread "main" java.lang.VerifyError: (class: GregorSamsa$0, method: test signature:         (IIIILcom/sun/org/apache/xalan/internal/xsltc/runtime/AbstractTranslet;Lcom/sun/org/apache/xml/internal/dtm/DTMAxisIterator;)Z) Incompatible type for getting or setting field
        at GregorSamsa.applyTemplates()
        at GregorSamsa.applyTemplates()
        at GregorSamsa.transform()
        at         com.sun.org.apache.xalan.internal.xsltc.runtime.AbstractTranslet.transform(AbstractTranslet.java:609)
        at com.sun.org.apache.xalan.internal.xsltc.trax.TransformerImpl.transform(TransformerImpl.java:729)
        at         com.sun.org.apache.xalan.internal.xsltc.trax.TransformerImpl.transform(TransformerImpl.java:340)
        at XML2JSON.cutXML(XML2JSON.java:105)
        at XML2JSON.main(XML2JSON.java:31)

You said you transformed it via a browser - does that mean you've run that same XSLT transformation successfully on the same documents outside your Java code? If so, it sounds like an XSLT "engine" difference. Wild guess - try inserting the <?xml version="1.0"?> at the front of your Java string. — Rob I
– Rob I, Commented Apr 27, 2012 at 13:51
Hi Rob, yes, I put <?xml-stylesheet type="text/xsl" href="test.xsl"?> at the beginning of my xml where test.xsl is the stylesheet, and applied it in google chrome and it worked just fine... by java string, do you mean my xml string or xsl string? — Piotr
– Piotr, Commented Apr 27, 2012 at 15:15
I mean the XSL string - it's XML as well after all, so I can imagine one XSL mechanism requiring that declaration at the beginning of the XSL document, but another not requiring it. — Rob I
– Rob I, Commented Apr 27, 2012 at 16:50
Well, I tried this with a quick program, and my Transformer did not require that declaration. That's with java 1.6 and 1.7. So it doesn't sound like the declaration was the issue, but it's promising that the exact same code worked fine with my XSL and XML. Is there any way you could dump out the XSL and XML to a file/log and try it independent of glassfish? — Rob I
– Rob I, Commented Apr 27, 2012 at 17:23
Hi Rob, when i run it externally, I get the following error when I run the above Java code - please see the edit on my original question :) — Piotr
– Piotr, Commented Apr 27, 2012 at 17:41

Mads Hansen · Accepted Answer · 2012-04-27 00:50:58Z

0

Content is not allowed in prolog. usually means that you have content before the start of your XML. The XML parser expects to either see the XML declaration: <?xml version="1.0"?>, or if that is omitted, then just the start of the document element (i.e. <sear:SEGMENTS>)

Print/log the content of this.xml and verify that there are no leading whitespace characters or other content before the XML declaration or document element.

answered Apr 27, 2012 at 0:50

Mads Hansen

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3 Comments

Piotr Over a year ago

Hi Mads, Thanks, but I've checked and no whitespace precedes the beginning of the document...

Mads Hansen Over a year ago

Of thae physical file, or your this.xml variable? Are you sure that your this.xml has the XML content? The error message references file:/root/webglassfish3/glassfish/domains/domain1/config/. Is that an error from another portion of your code, or could you be assigning the wrong information in String xmlSourceResource = this.xml;?

Piotr Over a year ago

Hey Mads, this.xml is just a string containing the XML content generated by a RESTFUL service's response to a search query. I'd checked and it does contain the XML...

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