Apex callout to a REST service - translate from Python

Question

I have a Python program that performs a REST API call:

def get_token(self):

        try:
            target_url = 'http://auth-{0}-{1}.{2}{3}/token'.format(
                self.country,
                self.environment,
                self.domain_pref,
                self.domain
                )
            
            payload = {
                'username': keys[self.project][self.environment]['username'],
                'password': keys[self.project][self.environment]['password'],
                'client_id': keys['client_id'],
                'client_secret': keys['client_secret'],
                'grant_type' : 'password'
                    }

            headers = {'Cache-Control': 'no-cache'}
            response = requests.post(target_url, data=payload,headers=headers)
            token = '{0} {1}'.format('Bearer',response.json()['access_token'])
            return token
        except Exception as e:
            logging.error(response.status_code)
            logging.error(response.content)
            raise e

I translated the Python program to Apex. Running the Apex code returns 400:

        // oAuth2 client credentials
        String username = '[email protected]';
        String password = 'password';
        String clientId = 'myclientid';
        String clientSecret = 'myclientsecret';
        String reqbody = 'grant_type=password&client_id='+clientId+'&client_secret='+clientSecret+'&username='+username+'&password='+password;

        // AP token endpoint setup
        String tokenAPEndpoint = 'http://auth-{0}-live.mydomain.com/token';
        String formattedTokenEndpoint;
        String token;

            String[] formatArgumentsToken = new String[]{'mx'};
            formattedTokenEndpoint = String.format(tokenAPEndpoint, formatArgumentsToken);
            System.debug('URL ' + formattedTokenEndpoint);

            HttpRequest requestToken = new HttpRequest();
            requestToken.setEndpoint(formattedTokenEndpoint);
            requestToken.setHeader('Content-Type','application/json');
            requestToken.setBody(reqbody);
            requestToken.setMethod('POST');

            system.debug('grant_type set to:' + requestToken.getHeader('grant_type'));
            system.debug('client_secret set to:' + requestToken.getHeader('client_secret'));
            system.debug('username set to:' + requestToken.getHeader('username'));
            
            Http httpGetToken = new Http();
            HttpResponse responseToken = httpGetToken.send(requestToken);
            
            system.debug('Response' + responseToken);
            system.debug('notification body' + responseToken.getBody());

Any help as to how this supposed to be done would be greatly appreciated!

Answer 1

The big difference between the one that works (Py) and the one that doesn't (Salesforce) is the request body.

In the Python example, you have constructed a key-value map that correctly reads like JSON, whereas in the Salesforce example it looks more like you are writing URL parameters in the request body.

You will want create a Map<String,String> with your body parameters and serialise it to JSON, then use that JSON string as the request body.

An example here on how to serialise a map to JSON: Serialize a Map into a specific JSON object