Getting 400 response when using Delphi to get Microsoft Translation

Question

I had registered my Application at Azure, received a secret and successfully got an access token using TIdHTTP with my Delphi 2010:

paramsList := TStringList.Create;
paramsList.Add('grant_type=client_credentials');
paramsList.Add('client_id=<ClientID>');
paramsList.Add('client_secret=<ClientSecret>');
paramsList.Add('scope=http://api.microsofttranslator.com');
try
  Result := idHTTP.Post(uri, lParamList);
finally
  FreeAndNill(idHTTP);
  FreeAndNill(paramsList);
end;

I then extract the token part of the response using copy. Now, when I try to get the actual translation I receive a Bad Request error. Here is what I try:

idHTTP.Request.CustomHeaders.AddValue('Authorization', headers);
try
   stringResult := idHTT.Get('http://api.microsofttranslator.com/v2/Http.svc/Translate?text=Gracias%20a%20l%20vida&from=es&to=en');
finally
   FreeAndNil(idHTTP);
end;

I also failed getting a response using post:

paramList := TStiringList.Create;
paramList.Add('Authorization= Bearer ' + Token);
try
  idHTTP.Post(uri, paramList);
finally
...

Still same response - 400, Any thoughts?

Answer 1

First, the facts: When requesting an access token at Microsoft Translator you use Post and when accessing the API with the access token you use Get (Thanks @RemyLebeau). Now the code. The code above for receiving the access token works. So the code for getting the translation is also straight forward:

lHTTP.Request.CustomHeaders.FoldLines := false; // avoid split by white space
lHTTP.Request.CustomHeaders.AddValue('Authorization', 'Bearer ' + AuthKey);
myStream =  TStringStream.Create;
try
  lHTTP.Get(uri, stream);
  stream.Position := 0;
  Result := stream.ReadString(stream.size);
finally
  FreeAndNil(lHTTP);
  FreeAndNil(stream);
end;

Answer 2

Here is a working example Check out: //http://oauthdevconsole.cloudapp.net/PartialOAuth

unit MSTranslationv2;

interface

uses
  Classes, SysUtils,
  IdBaseComponent, IdComponent, IdTCPConnection, IdTCPClient,
  IdHTTP, IdIOHandler, IdIOHandlerSocket, IdIOHandlerStack, IdSSL,
  IdSSLOpenSSL;

type
    TMSTranslator = class(TComponent)
    IdHTTP: TIdHTTP;
    IdSSLIOHandlerSocketOpenSSL: TIdSSLIOHandlerSocketOpenSSL;
  private
    fSourceLanguage: string;
    fClientID: string;
    fClientSecret: string;
    fTargetLanguage: string;
    AuthKey : string;

    { Private declarations }
    function GetAuthorizationKey: string;
    procedure SetClientID(const Value: string);
    procedure SetClientSecret(const Value: string);
  public
    { Public declarations }
    constructor Create(AOwner: TComponent); override;
    destructor Destroy; override;

    function Translate(Text: string): string;

    property ClientID: string read fClientID write SetClientID;
    property ClientSecret: string read fClientSecret write SetClientSecret;
    property SourceLanguage: string read fSourceLanguage write fSourceLanguage;
    property TargetLanguage: string read fTargetLanguage write fTargetLanguage;
  end;

//http://oauthdevconsole.cloudapp.net/PartialOAuth
implementation

uses
  HTTPApp, DBXJSON, ComObj, Variants;

{ TMSTranslator }

constructor TMSTranslator.Create(AOwner: TComponent);
begin
  inherited;

  IdHTTP := TIdHTTP.Create(nil);
  IdSSLIOHandlerSocketOpenSSL := TIdSSLIOHandlerSocketOpenSSL.Create(nil);

  IdHTTP.Request.ContentType := 'application/x-www-form-urlencoded';
  idHTTP.HandleRedirects := True;
  IdHTTP.Request.CustomHeaders.FoldLines := false; // avoid split by white space
  IdHTTP.IOHandler := IdSSLIOHandlerSocketOpenSSL;
end;

destructor TMSTranslator.Destroy;
begin
  IdHTTP.Free;
  IdSSLIOHandlerSocketOpenSSL.Free;

  inherited;
end;

procedure TMSTranslator.SetClientID(const Value: string);
begin
  if fClientID <> Value then
    AuthKey:= '';

  fClientID := Value;
end;

procedure TMSTranslator.SetClientSecret(const Value: string);
begin
  if fClientSecret <> Value then
    AuthKey := '';

  fClientSecret := Value;
end;

function TMSTranslator.GetAuthorizationKey: string;
var
  StringList : TStringList;
  StringStream: TStringStream;
  LJsonObj : TJSONObject;
  LJsonValue : TJSONValue;
begin
  if AuthKey = '' then begin

    if fClientID = '' then
      raise Exception.Create('Property fClientID needs to be assigned.');

    if fClientSecret = '' then
      raise Exception.Create('Property fClientSecret needs to be assigned.');

    StringList := TStringList.Create;
    StringStream := TStringStream.Create('', TEncoding.UTF8);
    try
      StringList.Add('grant_type=client_credentials');
      StringList.Add('&client_id='+ HTTPEncode(fClientID) );
      StringList.Add('&client_secret='+ HTTPEncode(fClientSecret));
      StringList.Add('&scope='+ HTTPEncode('http://api.microsofttranslator.com'));
      StringStream.WriteString(StringList.text);

      IdHTTP.Request.CustomHeaders.Clear;
      result := idHTTP.Post('https://datamarket.accesscontrol.windows.net/v2/OAuth2-13', StringStream);

      LJsonObj := TJSONObject.ParseJSONValue(TEncoding.ASCII.GetBytes(result),0) as TJSONObject;
      try
        LJsonValue :=LJsonObj.Get('access_token').JsonValue;
        result := LJsonValue.Value;
      finally
        LJsonObj.Free;
      end;

    finally
      StringList.free;
      StringStream.free;
    end;
  end else
    result := AuthKey;
end;

function TMSTranslator.Translate(Text: string): string;
var
  XmlDoc: OleVariant;
  Node: OleVariant;
  StringStream : TStringStream;
  Url: string;
const
  Msxml2_DOMDocument = 'Msxml2.DOMDocument.6.0';
begin
  AuthKey := GetAuthorizationKey;

  if Text <> '' then begin
    if fSourceLanguage = '' then
      raise Exception.Create('Property fSourceLanguage needs to be assigned.');

    if fTargetLanguage = '' then
      raise Exception.Create('Property fTargetLanguage needs to be assigned.');

    Url := format('http://api.microsofttranslator.com/v2/Http.svc/Translate?text=%s&from=%s&to=%s', [HTTPEncode(Text), fSourceLanguage, fTargetLanguage]);

    IdHTTP.Request.CustomHeaders.Clear;
    IdHTTP.Request.CustomHeaders.AddValue('Authorization', 'Bearer ' + AuthKey);
    StringStream := TStringStream.Create('', TEncoding.UTF8);
    try
      IdHTTP.Get(Url, StringStream);
      StringStream.Position := 0;
      Result := StringStream.ReadString(StringStream.size);

      XmlDoc:= CreateOleObject(Msxml2_DOMDocument);
      try
        XmlDoc.Async := False;
        XmlDoc.LoadXML(Result);
        if (XmlDoc.parseError.errorCode <> 0) then
          raise Exception.CreateFmt('Error in Xml data: %s',[XmlDoc.parseError]);
        Node:= XmlDoc.documentElement;
        if not VarIsClear(Node) then begin
          Result:= XmlDoc.Text;
          if pos('TranslateApiExceptionMethod', result) >0 then
            Result := '';
        end;
      finally
        XmlDoc := Unassigned;
      end;
  end else
    result := '';
end;

====================

var
  MSTranslator: TMSTranslator;
begin
  MSTranslator := TMSTranslator.Create(nil);
  try
    MSTranslator.ClientID := 'YourClientIDHere';
    MSTranslator.ClientSecret := 'YourClientSecretHere';
    MSTranslator.SourceLanguage := 'en';
    MSTranslator.TargetLanguage := 'th';
    ShowMessage(MSTranslator.Translate('Hello'));
  finally
    MSTranslator.free;
  end;
end;