Jmeter: parameterization issue with request Body - jmeter

Question

I am sending the following request with one parameterization parameter ${id} and request looks like
Actual Message:
{"Data":"{\"Source\":\"#include <stdio.h>\\nint main()\\n{\\nint n;\\nprintf(\\\"Enter an integer\\\");\\nscanf(\\\"%d\\\", &n);\\nif (n%2 == 0)\\nprintf(\\\"Even\\\");\\nelse\\nprintf(\\\"Odd\\\");\\nreturn 0;\\n}\",\"Lang\":\"c\",\"callback_url\":\"callback_url_string\",\"cid\":\"159:60719:2667:${id}\"}","Action":"compile","TenantId":"159","UserId":"0","CID":"159:60719:2667:${id}","LanguageId":"25331"}
But while sending the request JMETER is altering the request (removing the few formats like \'s) and sends to the server and server responds with bad request response.
JMETER Sends like:
{"Data":"{\"Source\":\"#include <stdio.h>\nint main()\n{\nint n;\nprintf(\\"Enter an integer\\");\nscanf(\\"%d\\", &n);\nif (n%2 == 0)\nprintf(\\"Even\\");\nelse\nprintf(\\"Odd\\");\nreturn 0;\n}\",\"Lang\":\"c\",\"callback_url\":\"callback_url_string\",\"cid\":\"159:60719:2667:558019\"}","Action":"compile","TenantId":"159","UserId":"0","CID":"159:60719:2667:558019","LanguageId":"25331"}
IF you send above request without parameterization (enter values) then it works fine.
Please let me know how to resolve this issue.

Answer 1

I am assuming this is a POST HTTP request and the body section has this data
could you please point the HTTP body to below relative path starts from bin directory
${__eval(${__FileToString(path/to/payloadfile.txt,,)})}
Now payloadfile.txt can have the actual content still it will evaluate ${ID} and further variables as well.
if that helps dont forget to click answered. Happy to help, Happy Testing
REFINE:
I have used online tools :
first to see the data in the fisrt place is a proper one https://jsonformatter.curiousconcept.com/
I see this
{
"Data":{
"Source":"#include <stdio.h\/>\r\n int main()\r\n {\r\n int n;\r\n printf(\"Enter an integer\");\r\n scanf(\"%d\", &n);\r\n if (n%2 == 0)\r\n printf(\"Even\");\r\n else\r\n printf(\"Odd\");\r\n return 0;\r\n "
},
"Lang":"c",
"callback_url":"callback_url_string",
"cid":"159:60719:2667:${id}",
"Action":"compile",
"TenantId":"159",
"UserId":"0",
"CID":"159:60719:2667:${id}",
"LanguageId":"25331"
}
I separated out C program alone
#include <stdio.h/>
int main()
{
int n;
printf("Enter an integer");
scanf("%d", &n);
if (n%2 == 0)
printf("Even");
else
printf("Odd");
return 0;
}
and applied escape characters using online tool [applied java script escape]
http://www.freeformatter.com/javascript-escape.html#ad-output
output:
#include <stdio.h\/>\r\n int main()\r\n {\r\n int n;\r\n printf(\"Enter an integer\");\r\n scanf(\"%d\", &n);\r\n if (n%2 == 0)\r\n printf(\"Even\");\r\n else\r\n printf(\"Odd\");\r\n return 0;\r\n }
this the one i used and it shown valid json document. if you are not sending valid json document server will throw error. do not select encoding in HTTP sampler