Requirement : I Want to enable debugging for validating data in Abap mapping level.
Step 1 : Get the input payload( In my case I am getting input payload from SXMB_MONI).
Step3 : Go to SE24 and select Abap-class.
Click Execute method and place external debugging breakpoint like below.
Step4 :Go to SXI_MAPPING_TEST tcode and provide all the details.
Then upload input payload and click on Execute button.
Now debugging enabled for Abap-class.
For above requirement I am referring below blog.
Hope this will be helpful.