Delphi使用Indy、ICS组件读取网页

使用Indy 10中TIdHTTP的例子：

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
  .
  .
  .
  Tick := GetTickCount;
  try
    try
      HttpClient.GetASync;
      while HttpClient.State <> httpReady do
      begin
        if GetTickCount - Tick > 30*1000 then
        begin
          HttpClient.Abort;
          Exit;
        end;
        Application.ProcessMessages;
      end;
  .
  .
  .