I am having trouble writing an Apex class that integrates to a non-SOAP based XML-over-HTTPS web service.  The problem is that the API requires an HTTP request parameter (not a header) to be set.  Here is their documentation on this:

"To implement the XML Data Integration Toolkit in an application, user must post the request to the Data Integration server with the XML request in a specific parameter.

• Data Integration server URL: https://toolkit.dnb.com/access/scripts/broker.asp
• Parameter name: request"

I naively hoped that the following code would work in an Apex class to access this API (since the HttpRequest Apex class does not have a setParameter() or setField() method -- like the equivalent Java or C# request classes do -- just the setHeader() method):

    public static String getLookupResponse() {
        Http h = new Http();
        HttpRequest req = new HttpRequest();
        req.setEndpoint('https://toolkit.dnb.com/access/scripts/broker.asp');
        req.setMethod('POST');
        req.setTimeout(60000);
        req.setBody(m_lookupTemplate);
        HttpResponse res = h.send(req);
        return res.getBody();
    }

where m_lookupTemplate is like the following (which works in their test harness HTML page):

<?xml version='1.0' encoding='UTF-8' ?>
<DGX>
  <SIGNONMSGSRQV1>
    <SONRQ>
      <DTCLIENT>2009-04-04 10:49:28</DTCLIENT>
      <USERID>craigmiled</USERID>
      <USERPASS>XXXXXXXXX</USERPASS>
      <LANGUAGE>EN</LANGUAGE>
      <FI>
        <ORG>DUN and BRADSTREET</ORG>
      </FI>
      <APPID>XML dnbToolkit</APPID>
      <APPVER>0010</APPVER>
    </SONRQ>
  </SIGNONMSGSRQV1>
  <CREDITMSGSRQV2>
    <LOOKUPTRNRQ>
      <TRNUID>242DF2924CC46</TRNUID>
      <LOOKUPRQ>
        <CTRY_CD>US</CTRY_CD>
        <PRIM_NME>Caterpillar</PRIM_NME>
        <TLCM_NBR></TLCM_NBR>
        <ADR_LINE></ADR_LINE>
        <NON_POST_TOWN></NON_POST_TOWN>
        <POST_TOWN></POST_TOWN>
        <PRIM_GEO_AREA>IL</PRIM_GEO_AREA>
        <POST_CODE></POST_CODE>
        <DUNS_NBR></DUNS_NBR>
        <REGN_NBR></REGN_NBR>
        <FILE_ID></FILE_ID>
        <RTN_MAX></RTN_MAX>
        <PURC_REAS_CD></PURC_REAS_CD>
        <MTCH_TYPE></MTCH_TYPE>
      </LOOKUPRQ>
    </LOOKUPTRNRQ>
  </CREDITMSGSRQV2>
</DGX>

This does not work as the server returns an "invalid request" result.

I tried setHeader('request',m_lookupTemplate) on HttpRequest instead of setBody().  No luck.  The basic problem is that HttpRequest does not allow you to programatically set request parameters.  Any ideas?

Thanks!

Dave