OnHTTPError event
HTTP Status Codes
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OnHTTPError event
HTTP Status Codes |
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| WinHTTP component.
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| type
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| TWinHTTPErrorEvent = procedure(Sender: TObject;
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| ErrorCode: Integer; Stream: TStream) of object;
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| property OnHTTPError: TWinHTTPErrorEvent;
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| The OnHTTPError event occurs if some error code has received in the header of response from HTTP server.
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| ErrorCode parameter contains the number which identifies the HTTP error (see the list of HTTP Status Codes to recognize an error).
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| Stream contains the error page generated by server.
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 Most often errors is 404 (requested document not found), 403 (view forbidden) and 500 (CGI script failed).
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 To handle error #401 (Access denied / Password required required to access) — write OnPasswordRequest event handler. (If OnPasswordRequest event handler exists, OnHTTPError will not occurs on error 401.)
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| Alternatively you can get HTTP error code in OnHeaderInfo event handler and decide whether to continue download (error page), or not, so this will save some client's bandwidth from downloading error page from server.
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 If it returns 0 in ErrorCode paramter, this means that component for some reason is unable to determinate the status code of HTTP query. However this is not always means fatal error like OnHostUnreachable. It's possible that server simply did not sent the status code in the header of response.
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| Delphi:
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| procedure TForm1.WinHTTP1HTTPError(Sender: TObject;
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| ErrorCode: Integer; Stream: TStream);
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| var
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| Str: String;
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| begin
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| with Stream as TMemoryStream do
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| if OutToMemo1.Checked then
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| begin // Output to Memo1
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| SetLength(Str, Size);
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| Move(Memory^, Str[1], Size);
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| Memo1.Text := Str;
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| end
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| else // Save to file
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| begin
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| Memo1.Text := 'Saved to c:\httptest.dat';
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| SaveToFile('c:\httptest.dat');
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| end;
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| case ErrorCode of
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| 404: Str := '404: Document not found';
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| 500: Str := '500: CGI script failed';
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| else // Mysterious reason
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| Str := IntToStr(ErrorCode);
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| end;
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| if (ErrorCode = HTTP_STATUS_OK) or (ErrorCode = HTTP_STATUS_PARTIAL_CONTENT) then // consts from WinInet.pas
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| begin
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| ContinueDownload := False;
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| Exit;
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| end;
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| StatusBar1.Panels[0].Text := 'HTTP Error #' + Str;
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| end;
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| C++ Builder:
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| void __fastcall TForm1::WinHTTP1HTTPError(TObject *Sender,
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| int ErrorCode, TStream *Stream)
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| {
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| AnsiString Str;
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| if (OutToMemo1->Checked) { // Output to Memo1
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| Str.SetLength(Stream->Size);
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| Move(((TMemoryStream*)Stream)->Memory, &Str[1], Stream->Size);
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| Memo1->Text = Str;
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| }else { // Save to file
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| Memo1->Text = "Saved to c:\httptest.dat";
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| ((TMemoryStream*)Stream)->SaveToFile("c:\httptest.dat");
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| }
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| switch (ErrorCode) {
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| case 404: Str = "404: Document not found";
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| case 500: Str = "500: CGI script failed";
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| default: Str = IntToStr(ErrorCode); // Mysterious reason
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| };
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| StatusBar1->Panels->Items[0]->Text = "HTTP Error #" + Str;
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| }
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| HTTP Status Codes
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| OnHeaderInfo, OnPasswordRequest, OnAnyError and OnDone events.
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