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 := ;
      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 > * 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 := ;

      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