Hi Raj,
Typically this is the sequence in which you use the transformation and invoke the backend if using JSON as input.
-> Transform JSON request to XML using Apply JSON Transformation assertion
-> Transform the xml to target/backend compatible xml using Apply XSL Transformation
-> Route to HTTP(S)
-> Transform the response xml from back end to the xml structure expected by the caller using Apply XSL Transformation
-> Trim the transformed xml to knock-off the root tag
-> Transform XML response to JSON using Apply JSON Transformation
The above flow gives utmost flexibility while transforming from JSON to XML and back. Hope its clear.
Regards,
Trinath