Delphi使用Indy、ICS组件读取网页

使用Indy 10中TIdHTTP的例子：

代码

uses
IdHttp;
.
.
.
function HttpGet(const Url: string; var Html: string): Boolean;
var
HttpClient: TIdHTTP;
begin
Result := False;
HttpClient := TIdHTTP.Create(nil);
try
Html := HttpClient.Get(Url);
Result := True;
except
on e: Exception do
begin
end;
end;
HttpClient.Free;
end;

Indy采用的是同步I/O的方式，而且在连接超时控制方面存在bug，因此TIdHttp.Get()有时会发生陷入死锁无法返回的问题。

使用ICS中THttpCli的例子：

uses
HttpProt;
.
.
.
function HttpGet(const Url: string; var Html: string): Boolean;
var
HttpClient: THttpCli;
DataLen: Int64;
FailMsg: string;
begin
Result := False;
HttpClient := THttpCli.Create(nil);
HttpClient.URL := Url;
HttpClient.NoCache := True;
HttpClient.RcvdStream := TMemoryStream.Create;
try
try
HttpClient.Get;
DataLen := HttpClient.RcvdStream.Size;
SetLength(Html, DataLen);
HttpClient.RcvdStream.Position := 0;
HttpClient.RcvdStream.Read(PChar(Html)^, DataLen);
Result := True;
except
on E: EHttpException do
begin
FailMsg := Format('Failed : %d %s',
[HttpClient.StatusCode, HttpClient.ReasonPhrase]);
end else
raise;
end;
finally
HttpClient.RcvdStream.Free;
HttpClient.RcvdStream := nil;
HttpClient.Free;
end;
end;

ICS使用的是异步I/O，其TFtpClient组件有Timout属性可以对连接超时进行控制，而THttpCli组件没有。但可以采用在定时器中调用THttpCli.Abort()取消连接的方式控制超时，也可以显式调用异步方法：

var

HttpClient: THttpCli;

DataLen: Int64;

FailMsg: string;

Tick: Cardinal;

begin

Result := False;

HttpClient := THttpCli.Create(nil);

HttpClient.URL := Url;

HttpClient.NoCache := True;

HttpClient.RcvdStream := TMemoryStream.Create;

Tick := GetTickCount;

try

try

HttpClient.GetASync;

while HttpClient.State <> httpReady do //检测HTTP状态

begin

if GetTickCount - Tick > 30*1000 then //此处设置了30S超时，可根据需要修改此数值

begin

HttpClient.Abort;

Exit;

end;

Application.ProcessMessages;

end;

DataLen := HttpClient.RcvdStream.Size;

SetLength(Html, DataLen);

HttpClient.RcvdStream.Position := 0;

HttpClient.RcvdStream.Read(PChar(Html)^, DataLen);

Result := True;

except

on E: EHttpException do

begin

FailMsg := Format('Failed : %d %s',

[HttpClient.StatusCode, HttpClient.ReasonPhrase]);

end else

raise;

end;

finally

HttpClient.RcvdStream.Free;

HttpClient.RcvdStream := nil;

HttpClient.Free;

end;

end