对
this question的回答表明,在delphi中通过类型库导入使用WinHTTP是多么容易.
我为WinHTTP导入了类型库,然后尝试使用该API编写文件下载帮助程序函数.这是我有多远：
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.
// 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,wr);
finally
FileStream := nil;
fs.Free;
end;
end;
except
result := false;
// do not raise exceptions.
end;
end;
摘自WinHTTP_TLB.pas：
IWinHttpRequest = interface(IDispatch)
['{016FE2EC-B2C8-45F8-B23B-39E53A75396B}']
......
property ResponseStream: OleVariant read Get_ResponseStream;
更新：我现在在调用http.ResponseStream.CopyTo(…)时获得关于ole变体的运行时异常
EOleError 'Variant does not reference an automation object'.
解决方法
Warren,您必须使用
AxCtrls.TOleStream类来与
Classes.TFileStream通信响应流
这样的事情
IWinHttpRequest.ResponseStream -> TOleStream -> TFileStream
检查此示例代码
{$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,wr:Int64;
FStatus : Integer;
OleStream: TOleStream;
begin
try
wUrl := url;
http := CoWinHttpRequest.Create;
http.open('GET',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.