DataSnap 多層返回數據集分析FireDAC JSON

采用服務器返回數據，一種是返回字符串數據例如JSON，跨平台跨語言，任何語言調用都支持兼容，類似WEBService。

第二種是緊密結合c++builder語言，傳輸DataSet，可以是ClientDataSet，也可以是FDMemTable，或TDataSet，這類好處是DataSet本身包含了很多屬性，記錄集的狀態Insert/Modify/Delete，在服務端可以調用

不同的方法進行數據處理，客戶端也只需要把dataset對象賦值就展示到dbgrid里了。

序列化。

FDMemTable1有saveToFile(sfJson),雖然是json格式，但不能跨語言交流，只能fdMem.LoadFromFile才可解析。所以用這個json字符串是不通用的，只能RAD delphi/c++使用。

http://localhost:8083/datasnap/rest/TServerMethods1/GetDepartmentNamesJSON

 

一、跨平台純字符串

 

Tokyo 10.2.2有了TFDBatchMoveJSONWriter

https://community.embarcadero.com/blogs/entry/dataset-mapping-to-json-for-javascript-client-support-in-rad-studio-10-2-2

 

對返回的數據增刪改查。對應的方法就是Add/Delete/Update/Query，客戶端調用此方法就OK了。

數據集轉換依賴於TDBXReader、TDBXCommand、SQLConnection1。不能隨意轉換dataset為json。有個第三方的庫可以轉。

Serever

String GetPersonAll()

{

return "";字符串形式的JSON或XML格式

aReader:=aCommand . ExecuteQuery;

Result:=TDBXJSONTools . TableToJSON(aReader, 10 , True ).ToString;

}

Client

String DataSTR=srv->GetPersonAll();

對字符串解析JSON或XML，以DataSet展示就可以。

function TServerMethods1.GetData(SQL: String): String;
var
  aCommand: TDBXCommand;
  aReader: TDBXReader;
begin
  Result := '';
  aCommand := SQLConnection1.DBXConnection.CreateCommand; // 指定 SQLConnection1 連接數據庫
  try
    aCommand.Text := SQL; // 指定SQL語句
    aReader := aCommand.ExecuteQuery;
    Result := TDBXJSONTools.TableToJSON(aReader, 10, True).ToString;
  finally
    aCommand.Free;
  end;
end;

 

 用第三方庫SuperJson也可以。

 二、DataSet

http://blog.csdn.net/ddqqyy/article/details/6982164 利用TDBXDataSetReader實例化,傳輸的是TDBXReader

http://blog.csdn.net/ddqqyy/article/details/6174525 講的是返回dataset ClientDataSet1.Delta，TDataSetProvider，TSqlServerMethod，還用到了OleVariant

#include <Data.DBXCDSReaders.hpp>

 static void __fastcall CopyReaderToClientDataSet(Data::Dbxcommon::TDBXReader* Reader, Datasnap::Dbclient::TClientDataSet* Dataset);
 static Datasnap::Dbclient::TClientDataSet* __fastcall ToClientDataSet(TComponent* AOwner, Data::Dbxcommon::TDBXReader* Reader, bool AOwnsInstance);

C++中這些返回指針，怎么釋放一直沒想清楚。

 三、返回ClientDataSet1的OleVariant

int TServerMethods1::GetTableDataSet(String atableName, OleVariant adata)
{
   ClientDataSet1->Open();
   adata = this->ClientDataSet1->Data;
   return this->ClientDataSet1->RecordCount;

}

DataSetProvider1也有Data屬性。

OleVariant Data

DataSetProvider1->Data;

只能用ClientDataSet1，其他的數據集都沒有data屬性，有data屬性的FDQuery類型也不是OleVariant 。

ClientDataSet：OleVariant Data

FDQuery：_di_IFDDataSetReference Data 

 

四、返回TDBXReader 

TDBXReader  可以自己釋放內存，所以不必擔心內心釋放泄露的問題了。

 #include "Data.DBXCDSReaders.hpp"

TDBXReader* TServerMethods1::GetDSReader(String asql)
{
    TDBXCommand *cmd;
    TDBXReader *reader;
    TClientDataSet *cds;
    cmd = SQLConnection1.DBXConnection.CreateCommand;
    cmd->Text = asql;
    reader = cmd->ExecuteQuery();
    return reader;

   //or
    cds = TDBXClientDataSetReader::ToClientDataSet(NULL, reader, true);
    return new TDBXClientDataSetReader(cds, true);

}

 Client

 reader= CallProxy.GetDSReader();

TDBXClientDataSetReader::CopyReaderToClientDataSet(reader,cds);
cds->Open();

 

五、用ClientDataSet 

服務端：

fdquery

DataSetProvider1.DataSet=fdquery;

DataSetProvider1.Option.poAllowCommandText=true;

客戶端

SQLConnection1

TDSProviderConnection.sqlconnection=SQLConnection1

TDSProviderConnection.serverclassname =tServerMethods1

ClientDataSet.RemoteServer=DSProviderConnection1

ClientDataSet.providername =DataSetProvider1

ClientDataSet.open();

ok!

六、返回TFDJSONDataSets 

TFDJSONDataSets可以返回多個數據集。這個是以后的趨勢！REST Client，但是這個不能跨語言，客戶端只能用RAD的TFDJSONDataSetsReader解析。但依然不能跨語言，C#，java無法解析。
服務的沒有釋放TFDJSONDataSets總感覺有內存泄漏，調用1000次測試一下。
返回字符串沒有內存泄漏。

server

function TServerMethods1.GetJSONData: TFDJSONDataSets;
begin
  Result := TFDJSONDataSets.Create;
  if not FDMemTable1.Active then
    FDMemTable1.LoadFromFile('../../customer.fds')
  else
    FDMemTable1.Active := False;
  TFDJSONDataSetsWriter.ListAdd(Result, FDMemTable1);
end;

 

Client

var
  DSList: TFDJSONDataSets;
begin
  FDMemTable1.Close;
  DSList := ClientModule1.ServerMethods1Client.GetJSONData;
  FDMemTable1.AppendData(
      TFDJSONDataSetsReader.GetListValue(DSList, 0));
  FDMemTable1.Open;
end;

 or serverProxy eg

 FUnMarshal := TDSRestCommand(FGetDepartmentNamesCommand.Parameters[0].ConnectionHandler).GetJSONUnMarshaler;
 Result := TFDJSONDataSets(FUnMarshal.UnMarshal(FGetDepartmentNamesCommand.Parameters[0].Value.GetJSONValue(True)));

客戶端 也可以  FDMemTableDepartments.Data := TFDJSONDataSetsReader.GetListValue(LDataSetList, 0);

七、返回TJSONArray

未實行

八、返回FireDAC TJSONObject

此方法雖然返回了TJSONObject，但依然不能跨語言，C#，java無法解析。

DataSet2JsonObject 

DataSetsToJSONObject
從DataSet到TJsonObject
http://community.embarcadero.com/blogs/entry/cbuilder-xe6-multitier-database-app-with-firedac-json-reflection-40330

TJSONObject * TServerMethods1::GetDepartmentEmployeesJSON     ( System::UnicodeString AID )
{

    FDQueryDepartmentEmployees->Active = false;
    FDQueryDepartment->Active = false;
    FDQueryDepartment->Params->operator[ ]( 0 )->Value = AID;
    FDQueryDepartmentEmployees->Params->operator[ ]( 0 )->Value = AID;
    // Create dataset list
    TFDJSONDataSets * ds = new TFDJSONDataSets( );
    // Add departments dataset
    TFDJSONDataSetsWriter::ListAdd( ds, sDepartment, FDQueryDepartment );
    // Add employees dataset
    TFDJSONDataSetsWriter::ListAdd( ds, sEmployees,
        FDQueryDepartmentEmployees );
    TJSONObject * obj = new TJSONObject( );
    TFDJSONInterceptor::DataSetsToJSONObject( ds, obj );
    return obj;
}

 服務的沒有釋放TFDJSONDataSets總感覺有內存泄漏，調用1000次測試一下。
返回字符串沒有內存泄漏。

TFDJSONDataSets

C++Builder
http://blogs.embarcadero.com/pawelglowacki/2014/06/04/40330/

Delphi
http://blogs.embarcadero.com/fernandorizzato/index.php/2014/07/21/multi-tier-com-delphi-xe6-e-firedac-json-reflection/

http://www.cnblogs.com/hnxxcxg/p/4007876.html
http://www.cnblogs.com/hnxxcxg/p/4008789.html
http://www.kzx123.com/?p=105
http://blog.marcocantu.com/blog/delphi_xe5_update2_datasnap_firedac.html
D:\Users\Public\Documents\Embarcadero\Studio\15.0\Samples\Object Pascal\DataSnap\FireDACJSONReflect

 TFDJSONDataSets *dset;
 TFDJSONDataSetsReader * dsread;
 TFDJSONDataSetsWriter::ListAdd(dset, FDMemTable1);//FDQuery1

TFDJSONDataSets 是DataSet的集合,數據集的集合，可以持有多個DataSet。
FDQuery1,FDMemTable1其實也可以有多個數據集，也算是數據集的集合，取下一個數據集FDQuery1.NextRecordSet

  FireDAC默認是不支持多結果集返回的, 需要手動設置 FetchOptions.AutoClose := False;

下面sql返回2個數據集。
FDQuery1.SQL.Text := 'select * from orders; select * from customers';

Data.FireDACJSONReflect.hpp
返回值可以是 TFDJSONDataSets，TJSONObject*，TFDJSONDeltas
通過 TFDJSONInterceptor::DataSetsToJSONObject()把TFDJSONDataSets轉為TFDJSONDataSets。

 static bool __fastcall DataSetsToJSONObject(TFDJSONDataSetsBase* const ADataSets, System::Json::TJSONObject* const AJSONObject);
 static bool __fastcall JSONObjectToDataSets(System::Json::TJSONObject* const AJSONObject, TFDJSONDataSetsBase* const ADataSets);
 static int __fastcall ListApplyUpdates(TFDJSONDeltas* const ADeltaList, const System::UnicodeString AKey, Firedac::Comp::Client::TFDCustomCommand* const ASelectCommand, TFDJSONErrors* const AErrors = (TFDJSONErrors*)(0x0))/* overload */;
 static Firedac::Comp::Client::TFDAdaptedDataSet* __fastcall GetListValueByName(TFDJSONDataSets* const ADataList, const System::UnicodeString AName);

 

void __fastcall TForm2::FormCreate(TObject *Sender)
{

    //Server dataSet > JSONObj
    TFDJSONDataSets *dss;
    TFDJSONDataSetsWriter::ListAdd(dss, FDMemTable1);
    TFDJSONDataSetsWriter::ListAdd(dss, "employ", FDMemTable1);

    TJSONObject *jsobj = new TJSONObject();
    TFDJSONInterceptor::DataSetsToJSONObject(dss, jsobj);

    //Client JSONObject > dataSet
    std::auto_ptr<TFDJSONDataSets>LDataSets(new TFDJSONDataSets());
    TFDJSONInterceptor::JSONObjectToDataSets(jsobj, LDataSets.get());
    FDMemTable1->Active = false;
    TFDAdaptedDataSet * LDataSet = TFDJSONDataSetsReader::GetListValue(LDataSets.get(), 0);
    FDMemTable1->AppendData(*LDataSet);

    // client updateData
    TFDJSONDeltas *LDeltas;
    TFDJSONDeltasWriter::ListAdd(LDeltas, "a", FDMemTable1);
    TFDJSONInterceptor::DataSetsToJSONObject(LDeltas, jsobj);
    // dm->ServerMethods1Client->ApplyChangesDepartmentEmployeesJSON(LJSONObject);

    //Server  updata DataBase Server
    TFDJSONInterceptor::JSONObjectToDataSets(jsobj, LDeltas);
    TFDJSONErrors *errs;
    TFDJSONDeltasApplyUpdates::ListApplyUpdates(LDeltas, "a", FDQuery1->Command, errs)

}

 

更新還沒實驗好
  TFDAdaptedDataSet * LDataSet =  TFDJSONDataSetsReader::GetListValueByName(LDataSets.get(), sDepartment);
  // Update UI
  FDMemTableDepartment->Active = False;
  FDMemTableDepartment->AppendData(*LDataSet);

fdstoreproc 執行返回數據
  FDStoredProc1.Close;
  FDStoredProc1.Unprepare;
  FDStoredProc1.StoredProcName := 'TServerMethods1.QueryData';
  FDStoredProc1.Prepare;
  FDStoredProc1.ParamByName('sql').Value := 'select * from MyTable';
  FDStoredProc1.open;
  FDMemTable1.Close;
  FDMemTable1.Data := FDStoredProc1.Data

#include "Data.DBXCommon.hpp"
 TDBXCommand *FFindDataSetCommand;

內存釋放FreeOnExecute有此函數貌似安全了。

FreeOnExecute registers the object indicated by Value, and frees it the next time the command is executed, closed, or freed. 

 返回TDataSet*

TDataSet* __fastcall TServerMethods1Client::FindDataSet(System::UnicodeString sql)
{
    if (FFindDataSetCommand == NULL)
    {
        FFindDataSetCommand = FDBXConnection->CreateCommand();
        FFindDataSetCommand->CommandType = TDBXCommandTypes_DSServerMethod;
        FFindDataSetCommand->Text = "TServerMethods1.FindDataSet";
        FFindDataSetCommand->Prepare();
    }
    FFindDataSetCommand->Parameters->Parameter[0]->Value->SetWideString(sql);
    FFindDataSetCommand->ExecuteUpdate();
    TDataSet* result = new TCustomSQLDataSet(NULL, FFindDataSetCommand->Parameters->Parameter[1]->Value->GetDBXReader(False), True);
    result->Open();
    if (FInstanceOwner)
        FFindDataSetCommand->FreeOnExecute(result);
    return result;
}

 

 九、返回TJSONObject

server code

// Get a Department and all Employees in the department.  Return TJSONObject.
function TServerMethods1.GetDepartmentEmployeesJSON(const AID: string)
  : TJSONObject;
var
  LDataSets: TFDJSONDataSets;
begin
  LDataSets := GetDepartmentEmployees(AID);
  try
    Result := TJSONObject.Create;
    TFDJSONInterceptor.DataSetsToJSONObject(LDataSets, Result)
  finally
    LDataSets.Free;
  end;
end;

client code

TJSONObject* __fastcall TServerMethods1Client::FindDataSetJSObj(System::UnicodeString sql)
{
    if (FFindDataSetJSObjCommand == NULL)
    {
        FFindDataSetJSObjCommand = FDBXConnection->CreateCommand();
        FFindDataSetJSObjCommand->CommandType = TDBXCommandTypes_DSServerMethod;
        FFindDataSetJSObjCommand->Text = "TServerMethods1.FindDataSetJSObj";
        FFindDataSetJSObjCommand->Prepare();
    }
    FFindDataSetJSObjCommand->Parameters->Parameter[0]->Value->SetWideString(sql);
    FFindDataSetJSObjCommand->ExecuteUpdate();
    TJSONObject* result = (TJSONObject*)FFindDataSetJSObjCommand->Parameters->Parameter[1]->Value->GetJSONValue(FInstanceOwner);
    return result;
}

 

返回Stream

Result := FFileDownloadCommand.Parameters[1].Value.GetStream(FInstanceOwner);

 

update json

// Update department and employees using deltas.  TJSONObject parameter.
procedure TServerMethods1.ApplyChangesDepartmentEmployeesJSON(const AJSONObject
  : TJSONObject);
var
  LDeltas: TFDJSONDeltas;
begin
  LDeltas := TFDJSONDeltas.Create;
  TFDJSONInterceptor.JSONObjectToDataSets(AJSONObject, LDeltas);
  ApplyChangesDepartmentEmployees(LDeltas);
end;

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flrizzato/FireDACJSONReflectionXE7

FireDACJSONReflectionXE7/ServerMethodsUnit1.pas
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//
// FireDACJSONReflect demo
// Copyright (c) 1995-2013 Embarcadero Technologies, Inc.

// You may only use this software if you are an authorized licensee
// of Delphi, C++Builder or RAD Studio (Embarcadero Products).
// This software is considered a Redistributable as defined under
// the software license agreement that comes with the Embarcadero Products
// and is subject to that software license agreement.
//
unit ServerMethodsUnit1;

interface

uses System.SysUtils, System.Classes, Datasnap.DSServer, Datasnap.DSAuth,
  FireDAC.Stan.Intf, FireDAC.Stan.Option, FireDAC.Stan.Param,
  FireDAC.Stan.Error, FireDAC.DatS, FireDAC.Phys.Intf, FireDAC.DApt.Intf,
  FireDAC.Stan.Async, FireDAC.DApt, FireDAC.UI.Intf, FireDAC.VCLUI.Wait,
  FireDAC.Stan.Def, FireDAC.Stan.Pool, FireDAC.Phys, Data.DB,
  FireDAC.Comp.Client, FireDAC.Phys.IBBase, FireDAC.Phys.IB, FireDAC.Comp.UI,
  FireDAC.Comp.DataSet, Data.FireDACJSONReflect, System.JSON,
  FireDAC.Stan.StorageBin, FireDAC.Stan.StorageJSON, FireDAC.Phys.IBDef;

type
{$METHODINFO ON}
  TServerMethods1 = class(TDataModule)
    FDQueryDepartmentEmployees: TFDQuery;
    FDQueryDepartment: TFDQuery;
    FDQueryDepartmentNames: TFDQuery;
    FDGUIxWaitCursor1: TFDGUIxWaitCursor;
    FDPhysIBDriverLink1: TFDPhysIBDriverLink;
    FDConnectionEMPLOYEE: TFDConnection;
    FDStanStorageJSONLink1: TFDStanStorageJSONLink;
    FDQueryDepartmentDEPT_NO: TStringField;
    FDQueryDepartmentDEPARTMENT: TStringField;
    FDQueryDepartmentHEAD_DEPT: TStringField;
    FDQueryDepartmentMNGR_NO: TSmallintField;
    FDQueryDepartmentBUDGET: TBCDField;
    FDQueryDepartmentLOCATION: TStringField;
    FDQueryDepartmentPHONE_NO: TStringField;
    procedure DataModuleCreate(Sender: TObject);
  public
    { Public declarations }
    function EchoString(Value: string): string;
    function ReverseString(Value: string): string;

    // Strongly typed methods
    function GetDepartmentNames: TFDJSONDataSets;
    function GetDepartmentEmployees(const AID: string): TFDJSONDataSets;
    procedure ApplyChangesDepartmentEmployees(const ADeltaList: TFDJSONDeltas);

    // Equivalent TJSONObject methods (C++ compatible)
    function GetDepartmentNamesJSON: TJSONObject;
    function GetDepartmentEmployeesJSON(const AID: string): TJSONObject;
    procedure ApplyChangesDepartmentEmployeesJSON(const AJSONObject
      : TJSONObject);

    function FileDownload(sFileName: string): TStream;
    procedure FileUpload(fStream: TStream);
  end;
{$METHODINFO OFF}

implementation

{$R *.dfm}

uses System.StrUtils, System.Generics.Collections;

const
  sDepartment = 'Department';
  sEmployees = 'Employees';
  sDataDir = 'c:\temp\';

  // Get a Department and all Employees in the department.  Result TFDJSONDataSets.
function TServerMethods1.GetDepartmentEmployees(const AID: string)
  : TFDJSONDataSets;
begin
  // Clear active so that query will reexecute
  FDQueryDepartmentEmployees.Active := False;
  FDQueryDepartment.Active := False;
  FDQueryDepartment.Params[0].Value := AID;
  FDQueryDepartmentEmployees.Params[0].Value := AID;

  // Create dataset list
  Result := TFDJSONDataSets.Create;
  // Add departments dataset
  TFDJSONDataSetsWriter.ListAdd(Result, sDepartment, FDQueryDepartment);
  // Add employees dataset
  TFDJSONDataSetsWriter.ListAdd(Result, sEmployees, FDQueryDepartmentEmployees);
end;

// Get a Department and all Employees in the department.  Return TJSONObject.
function TServerMethods1.GetDepartmentEmployeesJSON(const AID: string)
  : TJSONObject;
var
  LDataSets: TFDJSONDataSets;
begin
  LDataSets := GetDepartmentEmployees(AID);
  try
    Result := TJSONObject.Create;
    TFDJSONInterceptor.DataSetsToJSONObject(LDataSets, Result)
  finally
    LDataSets.Free;
  end;
end;

// Update department and employees using deltas.  TFDJSONDeltas parameter.
procedure TServerMethods1.ApplyChangesDepartmentEmployees(const ADeltaList
  : TFDJSONDeltas);
var
  LApply: IFDJSONDeltasApplyUpdates;
begin
  // Create the apply object
  LApply := TFDJSONDeltasApplyUpdates.Create(ADeltaList);
  // Apply the department delta
  LApply.ApplyUpdates(sDepartment, FDQueryDepartment.Command);

  if LApply.Errors.Count = 0 then
    // If no errors, apply the employee delta
    LApply.ApplyUpdates(sEmployees, FDQueryDepartmentEmployees.Command);
  if LApply.Errors.Count > 0 then
    // Raise an exception if any errors.
    raise Exception.Create(LApply.Errors.Strings.Text);
end;

// Update department and employees using deltas.  TJSONObject parameter.
procedure TServerMethods1.ApplyChangesDepartmentEmployeesJSON(const AJSONObject
  : TJSONObject);
var
  LDeltas: TFDJSONDeltas;
begin
  LDeltas := TFDJSONDeltas.Create;
  TFDJSONInterceptor.JSONObjectToDataSets(AJSONObject, LDeltas);
  ApplyChangesDepartmentEmployees(LDeltas);
end;

procedure TServerMethods1.DataModuleCreate(Sender: TObject);
begin

end;

// Get all Departments.  Result TFDJSONDataSets.
function TServerMethods1.GetDepartmentNames: TFDJSONDataSets;
begin
  // Clear active so that query will reexecute
  FDQueryDepartmentNames.Active := False;

  Result := TFDJSONDataSets.Create;
  TFDJSONDataSetsWriter.ListAdd(Result, FDQueryDepartmentNames);
end;

// Get all Departments.  Result TFDJSONDataSets;
function TServerMethods1.GetDepartmentNamesJSON: TJSONObject;
var
  LDataSets: TFDJSONDataSets;
begin
  LDataSets := GetDepartmentNames;
  try
    Result := TJSONObject.Create;
    TFDJSONInterceptor.DataSetsToJSONObject(LDataSets, Result);
  finally
    LDataSets.Free;
  end;
end;

function TServerMethods1.EchoString(Value: string): string;
begin
  Result := Value;
end;

function TServerMethods1.FileDownload(sFileName: string): TStream;
var
  fFileStream: TFileStream;
begin
  fFileStream := TFileStream.Create(sDataDir + sFileName, fmOpenRead);
  Result := fFileStream;
end;

procedure TServerMethods1.FileUpload(fStream: TStream);
var
  fMemStream: TMemoryStream;
  BytesRead: integer;
  sFileName: string;
  Buffer: PByte;
const
  MaxBufSize = 1024 * 1024;
begin
  sFileName := sDatadir + 'file-to-upload-copy.jpg';
  DeleteFile(sFileName);

  if not FileExists(sFileName) then
  begin
    fMemStream := TMemoryStream.Create;
    try
      fStream.Seek(0, TSeekOrigin.soBeginning);
      fStream.Position := 0;

      GetMem(Buffer, MaxBufSize);
      repeat
        BytesRead := fStream.Read(Buffer^, MaxBufSize);
        if BytesRead > 0 then
          fMemStream.WriteBuffer(Buffer^, BytesRead);
      until BytesRead < MaxBufSize;
      fMemStream.Seek(0, TSeekOrigin.soBeginning);

      fMemStream.SaveToFile(sFileName);
    finally
      fMemStream.Free;
    end;
  end;
end;

function TServerMethods1.ReverseString(Value: string): string;
begin
  Result := System.StrUtils.ReverseString(Value);
end;

end.

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Delphi DataSet與JSON互轉

DataSetConverter4Delphi

https://github.com/ezequieljuliano/DataSetConverter4Delphi

 

用webmodule返回

https://community.embarcadero.com/blogs/entry/display-json-base64-images-created-in-c-builder-using-ext-js-in-browser

void __fastcall TWebModule_main::WebModule_mainWebActionItem1Action(TObject *Sender,
          TWebRequest *Request, TWebResponse *Response, bool &Handled)

function TServerConnMonitorMethodsClient.ReverseString(Value: string): string;
begin
  if FReverseStringCommand = nil then
  begin
    FReverseStringCommand := FDBXConnection.CreateCommand;
    FReverseStringCommand.CommandType := TDBXCommandTypes.DSServerMethod;
    FReverseStringCommand.Text := 'TServerConnMonitorMethods.ReverseString';
    FReverseStringCommand.Prepare;
  end;
  FReverseStringCommand.Parameters[0].Value.SetWideString(Value);
  FReverseStringCommand.ExecuteUpdate;
  Result := FReverseStringCommand.Parameters[1].Value.GetWideString;
end;