I am getting below error the HTTP POST the Apex in salesforce

Question

Error: {"error":"unsupported_grant_type","error_description":"grant type not supported"}

Code:

String username     = '****@gmail.com';
String password     = '***********WwmQ***';
String endPoint     = 'https://test.salesforce.com/services/oauth2/token';
String clientid  = '****************';
String clientsecret = '****************8';
Http http = new Http();
HttpRequest req = new HttpRequest();
req.setEndpoint(endPoint);
req.setMethod('POST');
req.setHeader('Content-Type','application/json');
req.setBody('grant_type=password'+'&client_id='+clientid+'&client_secret='+clientsecret +'&username='+username+'&password='+password);
HttpResponse res = http.send(req);
System.debug('Body ' + res.getStatusCode());

Answer 1

I guess you are not appending security token to your password string.

Please check below article from Salesforce.

You must append the user’s security token to their password A security token is an automatically-generated key from Salesforce. For example, if a user's password is mypassword, and their security token is XXXXXXXXXX, then the value provided for this parmeter must be mypasswordXXXXXXXXXX. For more information on security tokens see “Reset Your Security Token” in the online help.

https://developer.salesforce.com/docs/atlas.en-us.api_rest.meta/api_rest/intro_understanding_username_password_oauth_flow.htm