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  • 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
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  • 原文地址:https://www.cnblogs.com/china1/p/3395033.html
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