将使用WinHTTP下载的文件保存到磁盘，使用Delphi XE

对this question的回答显示，通过delphi中的类型库导入来使用WinHTTP是多么容易。将使用WinHTTP下载的文件保存到磁盘，使用Delphi XE

我导入了WinHTTP类型库，然后尝试使用该API编写文件下载帮助函数。以下是我得到了多少：

我似乎无法弄清楚如何将IWinHttpRequest.ResponseStream（在TLB文件中声明为OleVariant）作为Stream保存到磁盘。从WinHTTP_TLB.pas

// IWinHttpRequest is defined by importing type library of WinHTTP. 
// Microsoft WinHTTP Services, version 5.1 (Version 5.1) C:\Windows\system32\winhttp.dll 
function Download(const url, filename: String): Boolean; 
var 
    http: IWinHttpRequest; 
    wUrl: WideString; 
    fs:TFileStream; 
    FileStream:IStream; 
    sz,rd,wr:Int64; 
begin 
    try 
    wUrl := url; 
    http := CoWinHttpRequest.Create; 
    http.open('GET', wurl, False); 
    http.send(EmptyParam); 

    FStatus := http.status; // 200=OK! 
    result := FStatus=200; 


    if result then 
    begin 
    fs := TFileStream.Create(filename, fmCreate, fmShareExclusive); 
    try 
     FileStream := TStreamAdapter.Create(fs, soReference) as IStream; 
     sz := http.ResponseStream.Size; 
     http.ResponseStream.CopyTo(FileStream,sz,rd,wr); 
    finally 
     FileStream := nil; 
     fs.Free; 
    end; 
    end; 
    except 
     result := false; 
     // do not raise exceptions. 
    end; 
end;

摘录：

IWinHttpRequest = interface(IDispatch) 
    ['{016FE2EC-B2C8-45F8-B23B-39E53A75396B}'] 
    ...... 
    property ResponseStream: OleVariant read Get_ResponseStream;

更新：我现在得到有关OLE变种运行时异常，在调用http.ResponseStream.CopyTo(...)

EOleError 'Variant does not reference an automation object'.

来源

2011-07-22 Warren P

相关：http://stackoverflow.com/questions/2771551/cast-object-as-olevariant-in-delphi –

TOleStream相关：http://stackoverflow.com/questions/4443376/how-to-free-tolestream-in-this-bit-of-code –

沃伦，你必须使用AxCtrls.TOleStream类将响应流与Classes.TFileStream

像这样

IWinHttpRequest.ResponseStream -> TOleStream -> TFileStream

入住此示例代码

{$APPTYPE CONSOLE} 

uses 
    Variants, 
    ActiveX, 
    Classes, 
    AxCtrls, 
    WinHttp_TLB, 
    SysUtils; 


function Download(const url, filename: String): Boolean; 
var 
    http: IWinHttpRequest; 
    wUrl: WideString; 
    fs:TFileStream; 
    HttpStream :IStream; 
    sz,rd,wr:Int64; 
    FStatus : Integer; 
    OleStream: TOleStream; 
begin 
    try 
    wUrl := url; 
    http := CoWinHttpRequest.Create; 
    http.open('GET', wurl, False); 
    http.send(EmptyParam); 

    FStatus := http.status; // 200=OK! 
    result := FStatus=200; 

    if result then 
    begin 
    HttpStream:=IUnknown(http.ResponseStream) as IStream; 
    OleStream:= TOleStream.Create(HttpStream); 
    try 
     fs:= TFileStream.Create(FileName, fmCreate); 
     try 
     OleStream.Position:= 0; 
     fs.CopyFrom(OleStream, OleStream.Size); 
     finally 
     fs.Free; 
     end; 
    finally 
     OleStream.Free; 
    end; 
    end; 

    except 
     result := false; 
     // do not raise exceptions. 
    end; 
end; 


begin 
    try 
    Download('http://foo.html','C:\Foo\anyfile.foo'); 
    except 
    on E: Exception do 
     Writeln(E.ClassName, ': ', E.Message); 
    end; 
end.

来源

2011-07-22 21:00:55 RRUZ

这很好。 –

将使用WinHTTP下载的文件保存到磁盘，使用Delphi XE

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