Unabled to retrieve response body of RestMessage API v2 Request

[Subramani3]

Hi Developers!

I am using RestMessgev2 for sending a POST API request to a Third-Party API endpoint in a Scoped Application.   I am able to successfully retrieve the response body when the HTTP Status Code is 200. However, I am receiving ClaimsService.getPrincipal() - Failed to fetch the user - 'ServiceNowTestUser' validation details 
when the HTTP Status Code is 400,403 etc (Failed).

Code Snippet:

var restAPI = new sn_ws.RESTMessageV2('<REST MESSAGE v2 Object Name>', 'GENERATE_ACCESS_TOKEN');

var endPoint = restAPI.getEndpoint();

endPoint = endPoint.replace('${baseUrl}', 'BASE URL GOES HERE');

restAPI.setEndpoint(endPoint);

var requestBody = "client_id=<CLIENT ID GOES HERE>" + "&client_secret=<CLIENT SECRET GOES HERE>" + "&username=ServiceNowTestUser" + "&password=<PASSWORD GOES HERE>" + "&grant_type=password";       

restAPI.setRequestBody(requestBody);

var response = restAPI.execute();

var responseBodyStr = response.getBody();

gs.info("Response: "+responseBodyStr) ;

It would be really great if you take a look at the issue and provide necessary resolution or workaround.

Thanks in advance!

[yashkamde · Accepted solution]

Hello @Subramani3 ,

try to get the actual failure reason from the third party:

var restAPI = new sn_ws.RESTMessageV2('<REST MESSAGE v2 Object Name>', 'GENERATE_ACCESS_TOKEN');

var endPoint = restAPI.getEndpoint().replace('${baseUrl}', 'BASE URL GOES HERE');
restAPI.setEndpoint(endPoint);

var requestBody = "client_id=<CLIENT ID>" +
    "&client_secret=<CLIENT SECRET>" +
    "&username=ServiceNowTestUser" +
    "&password=<PASSWORD>" +
    "&grant_type=password";

restAPI.setRequestBody(requestBody);

try {
    var response = restAPI.execute();
    var statusCode = response.getStatusCode();
    var responseBody = response.getBody();

    if (statusCode == 200) {
        gs.info("Success: " + responseBody);
    } else {
        gs.error("Third-party call failed. Status: " + statusCode +
                  " | Body: " + responseBody +
                  " | ErrorMsg: " + response.getErrorMessage());
    }
} catch (ex) {
    gs.error("RESTMessageV2 exception: " + ex.getMessage());
}

If my response helped mark as helpful and accept the solution.

[Subramani3]

Thank you so much for the reply. I am trying to get a 400 with an incorrect username and so that I can test the validation flow. I am not able to get the actual response which is sent by the API endpoint for 400.

When I try the API request in Postman with username incorrect intentionally then I am getting a 400 status code with the below details in the body. I am trying to retrieve the value in ServiceNow but unable to do so.

{

    "error": "invalid_request",

    "error_description": "The username and password you entered do not match an account in this organization."

I had also tried using the code which you shared and below is the output that I am receiving for getErrorMessage()

Method failed: (/AuthServices/Auth/connect/token) with code: 400