Delphi 调用http报错: IOHandler value is not valid

Delphi调用http服务报错，如下图：

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原因分析：

出现这种问题的原因是由于访问的url地址为https或存在其跳转地址为https。单纯使用idhttp是只能访问http，而https则需要搭配IdSSLIOHandlerSocketOpenSSL来实现对https的访问支持，还需要在系统目录或编译目标程序的同目录下有ssleay32.dll与libeay32.dll两个SLL协议的支持库。

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解决办法：

注意：此处需要Delphi7+indy10环境，主要逻辑如下，详细请参考代码。

var
    SSLIOHandler: TIdSSLIOHandlerSocketOpenSSL;
    HTTPClient: TIdHTTP;
begin
    SSLIOHandler := TIdSSLIOHandlerSocketOpenSSL.Create(nil);
    HTTPClient := TIdHTTP.Create(nil);
    try
        HTTPClient.IOHandler := SSLIOHandler;
        //其他代码
    finally
        HTTPClient.Free; 
        SSLIOHandler.Free;
    end;
end;

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参考代码如下：

uses
  IdBaseComponent, IdComponent, IdIOHandler,
  IdIOHandlerSocket, IdIOHandlerStack, IdSSL, IdSSLOpenSSL;

procedure TForm1.btn1Click(Sender: TObject);
var
  IdHttp:TIdHTTP;
  postUrl: string;
  postData: string;
  postStream:TStringStream;
  returnStream:TMemoryStream;
  inf_time: TDateTime;
  ret:boolean;
  oUrl, oJson,oPaasid, oToken, oNonce,oReturnStr,oEmgs: OleVariant;
  sJsonIn,sJsonOut :string;
  LStrings: TStringList;
  infcode,err_msg:string;  //返回值判断交易是否成功
  sPath,sDirectory:string;
  SSLIO: TIdSSLIOHandlerSocketOpenSSL;
begin
  sJsonIn := Memo1.Text;

  try
    IdHttp:=TIdHTTP.Create(nil);
    SSLIO := TIdSSLIOHandlerSocketOpenSSL.Create(nil);
    try
      IdHttp.HTTPOptions := IdHttp.HTTPOptions + [hoKeepOrigProtocol]; //必须有这行才使设置协议版本生效
      IdHTTP.Request.Accept := 'application/json';
      IdHTTP.Request.ContentType := 'application/json';
      IdHTTP.Request.ContentEncoding := 'utf-8';

      SSLIO.SSLOptions.Method:=sslvTLSv1;
      SSLIO.SSLOptions.Mode := sslmClient;
      IdHttp.IOHandler := SSLIO;

      postUrl := 'https://test.pub.**.com:8089/reg/yyds/mobile/api/amp/hos/getTradeFile';
      postData := sJsonIn;
      postStream := TStringStream.Create(UTF8Encode(postData));
      returnStream := TMemoryStream.Create;

      IdHTTP.Post(postUrl, postStream, returnStream);
      if returnStream = nil then
      begin
        ShowMessage('调用接口失败：下载文件失败！');
        Exit;
      end;

      sDirectory := ExtractFilePath(Application.ExeName);
      if not DirectoryExists(sDirectory) then
      begin
        CreateDirectory(PChar(sDirectory), nil);
      end;
      returnStream.SaveToFile(sDirectory + '\' + '1.ZIP');
    finally
      IdHttp.Free;
      postStream.Free;
      returnStream.Free;
      FreeAndNil(SSLIO);
    end;
  except
    on e:exception do
    begin
      showmessage('调用接口异常：'+e.message);
      Exit;
    end;
  end;
end;