DataSnap 多层返回数据集分析FireDAC JSON

采用服务器返回数据，一种是返回字符串数据例如JSON，跨平台跨语言，任何语言调用都支持兼容，类似WEBService。

第二种是紧密结合c++builder语言，传输DataSet，可以是ClientDataSet，也可以是FDMemTable，或TDataSet，这类好处是DataSet本身包含了很多属性，记录集的状态Insert/Modify/Delete，在服务端可以调用

不同的方法进行数据处理，客户端也只需要把dataset对象赋值就展示到dbgrid里了。

序列化。

一、跨平台纯字符串

对返回的数据增删改查。对应的方法就是Add/Delete/Update/Query，客户端调用此方法就OK了。

Serever

String GetPersonAll()

{

return "";字符串形式的JSON或XML格式

}

Client

String DataSTR=srv->GetPersonAll();

对字符串解析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 连接数据库
try
aCommand.Text := SQL; // 指定SQL语句
aReader := aCommand.ExecuteQuery;
Result := TDBXJSONTools.TableToJSON(aReader, 10, True).ToString;
finally
aCommand.Free;
end;
end;

用第三方库SuperJson也可以。

二、DataSet

http://blog.csdn.net/ddqqyy/article/details/6982164 利用TDBXDataSetReader实例化,传输的是TDBXReader
http://blog.csdn.net/ddqqyy/article/details/6174525 讲的是返回dataset ClientDataSet1.Delta，TDataSetProvider，TSqlServerMethod，还用到了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++中这些返回指针，怎么释放一直没想清楚。

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属性。

OleVariant Data

DataSetProvider1->Data;

只能用ClientDataSet1，其他的数据集都没有data属性，有data属性的FDQuery类型也不是OleVariant 。

ClientDataSet：OleVariant Data

FDQuery：_di_IFDDataSetReference Data

四、返回TDBXReader

TDBXReader 可以自己释放内存，所以不必担心内心释放泄露的问题了。

#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

服务端：

fdquery

DataSetProvider1.DataSet=fdquery;

DataSetProvider1.Option.poAllowCommandText=true;

客户端

SQLConnection1

TDSProviderConnection.sqlconnection=SQLConnection1

TDSProviderConnection.serverclassname =tServerMethods1

ClientDataSet.RemoteServer=DSProviderConnection1

ClientDataSet.providername =DataSetProvider1

ClientDataSet.open();

ok!

六、返回TFDJSONDataSets

TFDJSONDataSets可以返回多个数据集。这个是以后的趋势！REST Client
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)));

七、返回TJSONArray

未实行

八、FireDAC

FireDAC

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,数据集的集合，可以持有多个DataSet。
FDQuery1,FDMemTable1其实也可以有多个数据集，也算是数据集的集合，取下一个数据集FDQuery1.NextRecordSet

下面sql返回2个数据集。
FDQuery1.SQL.Text := 'select * from orders; select * from customers';

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

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flrizzato/FireDACJSONReflectionXE7

FireDACJSONReflectionXE7/ServerMethodsUnit1.pas
Git User on 15 Oct 2014 first version

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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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