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From Jan Hinzmann <...@geeksonly.de>
Subject cocoon as webservice (SOAP-Server)
Date Wed, 30 Mar 2005 08:59:05 GMT
Hi *,

I'm working on a little Webservice and I'm needing help on generating and
serializing xml-content from the flowscript to the sitemap and viceversa.

My approach is to generate a received SOAP-Envelope with a StreamGenerator and 
extracting the called method and the arguments using xslt and flow. Then I will 
be using the flowscript to compute the request and finally serialize an 
answer-envelope to the client.

For the ones of you who are in a hurry: go to the bottom of this mail to find my 
questions.


Let me introduce a (little) example (I'm sorry, it has become a bit bigger than 
I expected. But I hope it is worth reading it):

Imagine, there is a little Webservice, which has a echo-method:

public class Webservice(){
	public synchronised String echo(String echo){
		return echo;
	}
}

Now customers are sending SOAP-envelopes (using a middleware like axis) like the 
following:

   <?xml version="1.0" encoding="ISO-8859-1"?>
   <soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/"
xmlns:xsd="http://www.w3.org/2001/XMLSchema"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
     <soapenv:Body>
       <ns1:echo soapenv:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/"
xmlns:ns1="CodataWS">
         <ns1:arg0 xsi:type="xsd:string">Hello Echo!?</ns1:arg0>
       </ns1:echo>
     </soapenv:Body>
   </soapenv:Envelope>

this I'm generating with a org.apache.cocoon.generation.StreamGenerator and
forward it from the sitemap to the flowscript with:

<!-- == Webservice by Cocoon == -->
       <map:pipeline>
       	<map:match pattern="webservice">
       		<map:call function="mainWS"/>
       	</map:match>
	
	<!-- getting the soap-envelope -->
       	<map:match pattern="soapData">
       		<map:generate type="stream"/>
             <map:serialize type="xml"/>
       	</map:match>
...

The first matcher calls a flowscript, which will request the envelope and save 
it in an ByteArrayOutputStream using the second matcher:

   function mainWS(){
	var soapData     = new java.io.ByteArrayOutputStream();
	
	clog("SOAP-envelope received, processing the request:\n");
	
	//getting the envelope out of the request (can be done only once)
	cocoon.processPipelineTo("soapData", null, soapData);
	clog("Request was:\n" + soapData + "\n");
   ...

now that I have saved the soapData in an ByteArrayOutputStream, I'm sending it
back to the Sitemap, to get the Method out of the envelope ('echo' in this case) 
using xslt:

   var soapMethod   = new java.io.ByteArrayOutputStream();
   cocoon.processPipelineTo("soapMethod", {"soapData":soapData}, soapMethod);	
   clog("soapMethod: " + soapMethod + "\n");

OR
   var soapMethod   = new java.io.ByteArrayOutputStream();
   var pipeutil = 
cocoon.createObject(Packages.org.apache.cocoon.components.flow.util.PipelineUtil);
   pipeutil.processToStream("soapMethod",  {"soapData":soapData}, soapMethod);	
	
both methods seem to affect the same(?)

Back in the sitemap I've tried to generate this parameter with

   <!-- which Method is called? -->
   <map:match pattern="soapMethod">
     <map:generate type="stream" src="{flow-attribute:soapData}"/>
   ...

but that doesn't seem to work. Here (and generally :)) I would appreciate any 
suggestions!

For now I'm passing the content as parameter to the transformation:

   <!-- which Method is called? -->
   <map:match pattern="soapMethod">
     <map:generate src="xml/dummy.xml"/>
     <map:transform src="xsl/soapMethod.xsl">
       <map:parameter name="soapData" value="{flow-attribute:soapData}"/>
     </map:transform>
     <map:transform src="xsl/soapMethodNow.xsl"/>
     <map:serialize type="xml"/>
   </map:match>

the two stylesheets should extract the name of the method to be called (this 
will be found as local-name() in the first node after /Envelope/Body) and 
therefore looks like:

the first stylesheet should simply inject the soap-envelope-content soapMethod.xsl:

<?xml version="1.0"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
   <xsl:output method="xml"/>
   <xsl:param name="soapData"/>
	
   <xsl:template match="/">
	<xsl:value-of select="$soapData"/>
   </xsl:template>

</xsl:stylesheet>

and the second one should lookup the methodname
soapMethodNow.xsl:

<?xml version="1.0"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
	<xsl:output method="text"/>
	
	<xsl:template match="/Envelope/Body">
		<xsl:apply-templates/>
	</xsl:template>
	
	<xsl:template match="*[1]">
		<xsl value-of select="local-name()"/>
	</xsl:template>

</xsl:stylesheet>

strangely the first stylesheet produces output like:

  <?xml version="1.0" encoding="ISO-8859-1"?>
&lt;?xml version="1.0" encoding="ISO-8859-1"?&gt;
&lt;soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" 
xmlns:xsd="http://www.w3.org/2001/XMLSchema" 
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"&gt;
  &lt;soapenv:Body&gt;
   &lt;ns1:echo 
soapenv:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/" 
xmlns:ns1="CodataWS"&gt;
    &lt;ns1:arg0 xsi:type="xsd:string"&gt;Hello Echo!?&lt;/ns1:arg0&gt;
   &lt;/ns1:echo&gt;
  &lt;/soapenv:Body&gt;
&lt;/soapenv:Envelope&gt;

So why are the '<' and '>' are replaced with there corresponding htmlthingies?


What do you think about this approach?
Any suggestions are welcome.

-- 
Gruss, Jan Hinzmann




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