Delphi DataSnap - Change 'User-Agent' HTTP header property in client connections

Question

I have a Delphi XE2 Win32 app that connects to a REST service using DataSnap HTTP. The HTTP connection uses the default 'User-Agent' header of 'Mozilla/3.0 (compatible; Indy Library)'. I'd like to change this to be something more specific to my app so I can monitor connections on the server from different app editions. I'm using TDSRESTConnection to make the connection - can anybody point me to the object/property I need to work with to set the 'User-Agent'? I've tried using the following :

TDSRESTConnection.HTTP.Request.CustomHeaders.AddValue('User-Agent', 'MyText');

but this didn't make any difference.

Answer 1

Unfortunately, your custom headers are cleared and ignored in TDSRestRequest.GetHTTP (and TDSRestRequest is hidden in the implementation of Datasnap.DSClientRest unit). Try this workaround:

uses
  Datasnap.DSHTTP, IdHTTPHeaderInfo;

const
  SUserAgent = 'MyUserAgent';

type
  TDSHTTPEx = class(TDSHTTP)
    constructor Create(AOwner: TComponent; const AIPImplementationID: string); override;
  end;

  TDSHTTPSEx = class(TDSHTTPS)
    constructor Create(const AIPImplementationID: string); override;
  end;

{ TDSHTTPEx }

constructor TDSHTTPEx.Create(AOwner: TComponent; const AIPImplementationID: string);
begin
  inherited Create(AOwner, AIPImplementationID);
  with Request.GetObject as TIdRequestHeaderInfo do
    UserAgent := SUserAgent;
end;

{ TDSHTTPSEx }

constructor TDSHTTPSEx.Create(const AIPImplementationID: string);
begin
  inherited Create(AIPImplementationID);
  with Request.GetObject as TIdRequestHeaderInfo do
    UserAgent := SUserAgent;
end;

initialization
  TDSHTTP.UnregisterProtocol('http');
  TDSHTTP.RegisterProtocol('http', TDSHTTPEx);
  TDSHTTP.UnregisterProtocol('https');
  TDSHTTPS.RegisterProtocol('https', TDSHTTPSEx);

finalization
  TDSHTTP.UnregisterProtocol('http');
  TDSHTTP.UnregisterProtocol('https');

end.