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Lab: Write an XSLT Transform

Lab status

This lab is an outline with the key steps and a working stylesheet. Expand it as you experiment; it builds directly on Transform Actions (XSLT).

Goal: add a Transform action to your gateway policy that reshapes the request body before it reaches the backend.

Prerequisites: the echo-gateway MPGW; you're in the lab domain.

Step 1 — Write the stylesheet​

Save this as transform.xsl and upload it to local::

<xsl:stylesheet version="1.0"
    xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
    xmlns:dp="http://www.datapower.com/extensions"
    extension-element-prefixes="dp">
  <xsl:output method="xml" indent="yes"/>

  <xsl:template match="/request">
    <order>
      <id><xsl:value-of select="orderId"/></id>
      <customer><xsl:value-of select="customer/name"/></customer>
      <total><xsl:value-of select="amount"/></total>
    </order>
    <xsl:message dp:priority="info">transform.xsl ran</xsl:message>
  </xsl:template>
</xsl:stylesheet>

Step 2 — Set the message types​

On echo-gateway, set Request Type to XML (or JSON and add a Convert action first) so the body parses into a node tree the transform can process.

Step 3 — Add the Transform action​

  1. Edit echo-policy's request rule.
  2. Between the Match and the final Results action, drop a Transform action.
  3. Stylesheet: local:///transform.xsl.
  4. Wire it: input = the match's output context, output = a new context that feeds the Results action (don't leave it reading INPUT by mistake).
  5. Apply.

Step 4 — Test and verify​

curl -ik https://localhost:8443/orders \
  -H 'Content-Type: application/xml' \
  -d '<request><orderId>42</orderId><customer><name>Ada</name></customer><amount>99.50</amount></request>'

Use the Probe (Troubleshooting) to confirm the message is reshaped at the Transform action's output context.

Outline: expand this lab​

  • Convert JSON→XML first, then transform, then XML→JSON out.
  • Use dp:set-variable to also set the dynamic backend from the stylesheet.
  • Add a Validate action against an XSD before transforming.