Question

We have a RemObjects SDK HTTP server that exposes a number of services and methods. Is it possible to call a method via a URI rather than passing the parameters as SOAP/JSON e.g.

http://www.mywebservice.com/servicename/methodname?param1=xxx&param2=yyy

Answer 1

UPDATE

I’ve written an improved version of the server descendant. This one converts a formatted URI into a JSON object that will subsequently be handled by the RO JSON Message handler.

The default handing method is to ignore the URI.

Change URIHandlingMethod to urhJSON to accept a URI like this:

http://www.mywebservice.com/json?{JSON OBJECT}

Set URIHandlingMethod to urhParametersto to accept a URI like this:

http://www.mywebservice.com/json/service/method?param1=xxx&param2=yyy

Here’s the code:

unit ROJSONURIIndyHTTPServer ;

interface

uses
  SysUtils, Classes,

  uROIndyHTTPServer,

  IdURI, IdCustomHTTPServer;

type
  TURIHandlingMethod = (
    urhNone,
    urhJSON,
    urhParameters
  );

  TROJSONURIIndyHTTPServer = class(TROIndyHTTPServer)
  private
    FURIHandlingMethod: TURIHandlingMethod;
    FJSONVersion: String;

    function ConvertURIToJSON(const Document, Params: String): String;
    function NextBlock(var Value: String; Delimiter: Char = '/'): String;
  protected
    procedure InternalServerCommandGet(AThread: TIdThreadClass; RequestInfo: TIdHTTPRequestInfo; ResponseInfo: TIdHTTPResponseInfo); override;
  public
    constructor Create(AOwner: TComponent); override;
  published
    property URIHandlingMethod: TURIHandlingMethod read FURIHandlingMethod write FURIHandlingMethod;
    property JSONVersion: String read FJSONVersion write FJSONVersion;
  end;

implementation

{ TROJSONURIIndyHTTPServer }

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

  FJSONVersion := '1.1';
end;

function TROJSONURIIndyHTTPServer.NextBlock(var Value: String; Delimiter: Char): String;
var
  p: Integer;
begin
  p := 1;

  while (p <= length(Value)) and (Value[p] <> Delimiter) do
    Inc(p);

  if p = length(Value) then
    Result := Value
  else
    Result := copy(Value, 1, p - 1);

  Value := copy(Value, p + 1, MaxInt);
end;

function TROJSONURIIndyHTTPServer.ConvertURIToJSON(const Document, Params: String): String;
const
  JSONObjectTemplate = '{"method":"%s.%s"%s,"version": "%s"}';
  JSONParamTemplate = '"%s":"%s"';
  JSONParamsTemplate = ',"params":{%s}';
var
  CallService, CallMessage,
  ParsedDocument, ParsedParams, JSONParams,
  Param, ParamName, ParamValue: String;
  i: Integer;
begin
  Result := '';

  ParsedDocument := Trim(Document);

  // Remove the leading /
  if (length(Document) > 0) and
     (Document[1] = '/') then
    NextBlock(ParsedDocument);

  // Remove the message type
  NextBlock(ParsedDocument);

  // Extract the service
  CallService := NextBlock(ParsedDocument);

  // Exctract the service message (method)
  CallMessage := NextBlock(ParsedDocument);

  JSONParams := '';
  ParsedParams := Params;

  while ParsedParams <> '' do
  begin
    // Extract the parameter and value
    Param := NextBlock(ParsedParams, '&');

    // See RFC 1866 section 8.2.1. TP
    Param := StringReplace(Param, '+', ' ', [rfReplaceAll]);  {do not localize}

    // Extract the parameter name
    ParamName := NextBlock(Param, '=');

    // Extract the parameter value
    ParamValue := Param;

    // Add a delimiter if required
    if JSONParams <> '' then
      JSONParams := JSONParams + ',';

    // Build the JSON style parameter
    JSONParams := JSONParams + format(JSONParamTemplate, [ParamName, ParamValue]);
  end;

  if JSONParams <> '' then
    JSONParams := format(JSONParamsTemplate, [JSONParams]);

  // Make sure we have values for all the object variables, then build the JSON object
  if (CallService <> '') and
     (CallMessage <> '') and
     (FJSONVersion <> '') then
    Result := format(JSONObjectTemplate, [CallService, CallMessage, JSONParams, JSONVersion]);
end;

procedure TROJSONURIIndyHTTPServer.InternalServerCommandGet(
  AThread: TIdThreadClass; RequestInfo: TIdHTTPRequestInfo;
  ResponseInfo: TIdHTTPResponseInfo);
begin
  if FURIHandlingMethod in [urhJSON, urhParameters] then
  begin
    // Parse parameters into JSON if required
    if FURIHandlingMethod = urhParameters then
      RequestInfo.UnparsedParams := ConvertURIToJSON(RequestInfo.Document, RequestInfo.UnparsedParams);

    // Decode the URI e.g. converts %20 to whitespace
    RequestInfo.UnparsedParams := TIdURI.URLDecode(RequestInfo.UnparsedParams);

    //  This works around a bug in TROIndyHTTPServer. By adding a whitespace to the
    //  end of the QueryParams it forces the http server to process the parameters
    RequestInfo.QueryParams := TIdURI.URLDecode(RequestInfo.QueryParams) + ' ';
  end;

  inherited;
end;

end.

---

Original Answer

This is a follow up to André’s answer.

With the current version of RemObjects SDK the following URI should work, but doesn’t:

http://www.mywebservice.com/JSON?{"id":"{392543cf-f110-4ba3-95471b02ce5bd693}","method":"servicename.methodname","params":{"param1":"xxx","param2":"yyy"}}:

There are 2 reasons why:

• The URI is not decoded before it is passed to the message handler. This results in a JSON error if any of the characters have been encoded e.g. %20 etc.
• There seems to be a bug in the ROIndyHTTPServer code that mishandles the URI parameters.

I’ve created a ROIndyHTTPServer descendant that fixes both problems. Here’s the code:

unit FixedROIndyHTTPServer;

interface

uses
  SysUtils, Classes,

  uROIndyHTTPServer,

  IdURI, IdCustomHTTPServer;

type
  TFixedROIndyHTTPServer = class(TROIndyHTTPServer)
  protected
    procedure InternalServerCommandGet(AThread: TIdThreadClass; RequestInfo: TIdHTTPRequestInfo; ResponseInfo: TIdHTTPResponseInfo); override;
  public
    constructor Create(AOwner: TComponent); override;
  end;

implementation

{ TFixedROIndyHTTPServer }

constructor TFixedROIndyHTTPServer.Create(AOwner: TComponent);
begin
  inherited;
end;

procedure TFixedROIndyHTTPServer.InternalServerCommandGet(
  AThread: TIdThreadClass; RequestInfo: TIdHTTPRequestInfo;
  ResponseInfo: TIdHTTPResponseInfo);
begin
  // This fixes 2 issues with TROIndyHTTPServer
  //  1) It decodes the parameters e.g. converts %20 to whitespace
  //  2) It adds a whitespace to the end of the QueryParams. This
  //     forces the http server to process the parameters.

  RequestInfo.QueryParams := TIdURI.URLDecode(RequestInfo.QueryParams) + ' ';
  RequestInfo.UnparsedParams := TIdURI.URLDecode(RequestInfo.UnparsedParams);

  inherited;
end;

end.

This doesn’t answer my question, but it is a workaround for anybody having similar problems.

I’m still keen to hear if RO SDK supports the use of custom URIs.