Please check this blog for SICF configuration and Service handler class creation. In this example, passing the IDoc number through Params instead if Payload. Payload
JMeter, IDoc, XML & SAP
It can be useful for load testing / Performance testing in scenarios where we have to create multiple IDocs for test. API’s can also be
Program to retrieve XML Data from IDoc
Execute above code to get the XML Data from IDoc
Parsing XML to internal table in SAP without transformation
To parse the XML data into SAP Internal Tables, generally we write Transformation using TCode XSLT_TOOL and need to call that using CALL TRANSFORMATION keyword.