SAP APIM policy templates.

 https://api.sap.com/package/SecurityBestPractices/policytemplate

https://api.sap.com/package/SecurityBestPractices/policytemplate

https://github.com/SAP/apibusinesshub-api-recipes/blob/master/api-recipes-by-type.md

https://github.com/SAP/apibusinesshub-api-recipes/tree/master/authentication/basicauthentication

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Here’s a use case to transform an XML response format using the <XSL> policy in SAP BTP APIM. Suppose you have an API that returns a response in XML format but you need to transform it into another XML structure for downstream systems. This is where an XSLT transformation can be applied using the <XSL> policy.

Use Case: Transforming Product Data XML

Objective: Transform the XML response containing product details from the format provided by the source system to a new format required by the target system.

Scenario

• Input XML (from the source system):

  xml
  <ProductDetails>
      <Product>
          <ProductID>12345</ProductID>
          <ProductName>Wireless Mouse</ProductName>
          <Price>25.99</Price>
          <Availability>In Stock</Availability>
      </Product>
  </ProductDetails>
  

• Target XML (required by the target system):

  xml
  <Item>
      <ID>12345</ID>
      <Name>Wireless Mouse</Name>
      <Cost>25.99</Cost>
      <Status>In Stock</Status>
  </Item>
  

XSL Policy Implementation

1. Define the <XSL> Policy in the API proxy to transform the response XML.

   xml
   <XSL async="true" continueOnError="false" enabled="true" xmlns="http://www.sap.com/apimgmt">
       <!-- Output variable to store transformed XML -->
       <OutputVariable>transformedResponse</OutputVariable>
       <!-- Reference to the XSLT file for transformation -->
       <ResourceURL>xsl://ProductDataTransform.xsl</ResourceURL>
       <!-- Source message for transformation -->
       <Source>response</Source>
   </XSL>
   

2. XSLT Transformation (ProductDataTransform.xsl): This XSLT file will map elements from the source XML to the required target XML structure.

   xml
   <?xml version="1.0" encoding="UTF-8"?>
   <xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
       <xsl:output method="xml" indent="yes"/>
       
       <!-- Root element template match for ProductDetails -->
       <xsl:template match="/ProductDetails/Product">
           <Item>
               <!-- Mapping source elements to target elements -->
               <ID><xsl:value-of select="ProductID"/></ID>
               <Name><xsl:value-of select="ProductName"/></Name>
               <Cost><xsl:value-of select="Price"/></Cost>
               <Status><xsl:value-of select="Availability"/></Status>
           </Item>
       </xsl:template>
   </xsl:stylesheet>
   

Explanation of XSL Policy and XSLT Transformation

• OutputVariable: The transformed XML output is stored in the variable transformedResponse, which you can later use for further processing or to send as the API response.

• ResourceURL: The xsl://ProductDataTransform.xsl refers to the XSLT file uploaded in the API Management platform that performs the transformation.

• Source: This is set to response, which is the original XML response from the backend that you wish to transform.

Expected Output

After applying this transformation, the transformedResponse variable will contain the following XML structure:

xml
<Item>
    <ID>12345</ID>
    <Name>Wireless Mouse</Name>
    <Cost>25.99</Cost>
    <Status>In Stock</Status>
</Item>

This output can then be sent as the API response or used in further policies as needed.

Using this approach, the <XSL> policy in SAP BTP APIM enables flexible XML transformations to meet the specific needs of different client systems or backend services.

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How to debug api 

https://community.sap.com/t5/technology-blogs-by-members/demystifying-use-of-custom-script-in-sap-cloud-platform-api-management/ba-p/13377656

json schema validation

https://community.sap.com/t5/technology-blogs-by-members/validate-json-message-in-api-management/ba-p/13523122

hands on required 

https://sapzero2hero.com/2023/01/03/sap-cpi-working-with-policy-in-sap-api-management-part-01/

https://signatov.com/handling-exceptions-when-triggering-the-sap-btp-api/  very importtant.

https://saurabhtree.com/2024/03/03/sap-api-management-part-4-managing-apis/comment-page-1/