public class RestApiCall{
public HTTPResponse res {get; set;}
public String resBody {get; set;}
//public String token{get; set;}
public String st{get; set;}
public String endpoint {get; set;}

public String token {
      get{

              token = '......f25aaf810';

          return token;
      }
      set;
}

public String dns{
      get{

              dns= 'sb-....veevavault.com';

          return dns;
      }
      set;
}
// incvoke callout to selected external webservice

public static void submit() {
//String token ='....-a52e76cb-0bca-42de-8b9f.......';

// Post HttpRequest 1
HttpRequest req = new HttpRequest();
//Set HTTPRequest Method
req.setMethod('POST');
req.setHeader('content-type', 'application/json');
req.setEndpoint('https://sb-.....veevavault.com/api/v17.1/auth?username=______&password=_____');

Http http = new Http();

try {

//Execute web service call here
HTTPResponse res = http.send(req);
String st = res.toString();
//Helpful debug messages
System.debug('Response@'+st);
System.debug('STATUS:'+res.getStatus());
System.debug('STATUS_CODE:'+res.getStatusCode());

} catch(System.CalloutException e) {
//Exception handling goes here....
System.debug(e);
}

//Post HttpRequest 2

HttpRequest req2 = new HttpRequest();
//Set HTTPRequest Method
req2.setMethod('POST');
req2.setHeader('Authorization', 'FBE52618EF223460F0F87F71A26DFE22155C760191E9.......F2EB99D7D9BA91BF8EDBC7EBA072....');
req2.setEndpoint('https://sb-.....-ae.veevavault.com/api/v17.1/objects/documents/tokens?docIds=XXXX');

Http http2 = new Http();

try {

//Execute web service call here
HTTPResponse res2 = http2.send(req2);
String st2 = res2.toString();
//Helpful debug messages
System.debug('Response@'+st2);
System.debug('STATUS:'+res2.getStatus());
System.debug('STATUS_CODE:'+res2.getStatusCode());

} catch(System.CalloutException e) {
//Exception handling goes here....
System.debug(e);
}


}
}