Solved: Best way to Mashup content from multiple distinct ... - Page 2

DChiesa · 03-30-2016 09:08 PM

Question for the practitioners here.

If you wanted to retrieve and then mash-up 3 distinct XML documents within an API Proxy, how would you do it?

I can think of multiple ways.

- write a Java callout to do the work, relying on org.w3c.dom.Document etc

- rely on XSLT and the document() function to retrieve stuff from within XSLT, then use xsl:copy-of

- use nodejs and whatever XML parser is available there to prune-graft elements together.

There are probably others. Which approach would you use and why?

DChiesa

Here's one way to do it: using the document() function in xslt. This function loads a document from a URL. So, set the URLs in a prior policy, then pass those locations into the XSLT as parameters, then mash them up like so:

(In this example, the documents in question are FHIR documents. )

<xsl:stylesheet version="1.0"
                xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
                xmlns:fhir="http://hl7.org/fhir">

  <xsl:output indent="yes"/>
  <xsl:strip-space elements="*"/>

  <!-- these are parameters set in the XSL Policy config -->
  <xsl:param name="loc1" select="''"/>
  <xsl:param name="loc2" select="''"/>
  <xsl:param name="loc3" select="''"/>

  <!-- the following retrieves the remote documents into variables
       available to the stylesheet -->
  <xsl:variable name="xdoc1" select="document($loc1)"/>
  <xsl:variable name="xdoc2" select="document($loc2)"/>
  <xsl:variable name="xdoc3" select="document($loc3)"/>


  <xsl:template match="/">
    <!-- Mashup 3 FHIR documents -->
    <!-- for now, we omit the link (self, next) elements -->
    <Bundle xmlns="http://hl7.org/fhir">
      <xsl:copy-of select="$xdoc1/fhir:Bundle/fhir:entry"/>
      <xsl:copy-of select="$xdoc2/fhir:Bundle/fhir:entry"/>
      <xsl:copy-of select="$xdoc3/fhir:Bundle/fhir:entry"/>
    </Bundle>
  </xsl:template>

</xsl:stylesheet>

The XSL Policy might look like this:

<XSL name='XSL-Mashup'>
  <DisplayName>XSL-Mashup</DisplayName>
  <Source>dummyRequest</Source>
  <OutputVariable>response.content</OutputVariable>
  <ResourceURL>xsl://mashup.xsl</ResourceURL>
  <Parameters ignoreUnresolvedVariables='true'>
    <Parameter name='loc1' ref='loc1'/>
    <Parameter name='loc2' ref='loc2'/>
    <Parameter name='loc3' ref='loc3'/>
  </Parameters>
</XSL>

There is a dummyRequest (Message object) because I don't want the XSL to use what's in the request. I want to only grab some external content. Each of loc1, loc2, loc3 carry a string which is a url that will return an XML document.

This works only when there is no security on the FHIR / XML endpoints.

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Best way to Mashup content from multiple distinct XML documents?