c++builder调用delphi编写的datasnap程序的问题
delphi编写datasnap服务器
new datasnap server向导
unit ServerContainerUnit1;

interface

uses
SysUtils, Classes,
DSTCPServerTransport,
DSServer, DSCommonServer;

type
TServerContainer1 = class(TDataModule)
DSServer1: TDSServer;
DSTCPServerTransport1: TDSTCPServerTransport;
DSServerClass1: TDSServerClass;
procedure DSServerClass1GetClass(DSServerClass: TDSServerClass;
var PersistentClass: TPersistentClass);
private
{ Private declarations }
public
end;

var
ServerContainer1: TServerContainer1;

implementation

uses Windows, ServerMethodsUnit1;

{$R *.dfm}

procedure TServerContainer1.DSServerClass1GetClass(
DSServerClass: TDSServerClass; var PersistentClass: TPersistentClass);
begin
PersistentClass := ServerMethodsUnit1.TServerMethods1;
end;

end.



unit ServerMethodsUnit1;

interface

uses
SysUtils, Classes, DSServer, DBXJSON;

type
TServerMethods1 = class(TDSServerModule)
private
{ Private declarations }
public
{ Public declarations }
pecho: TDBXCallback;

function EchoString(Value: string): string;
procedure reg_echo(pecho: TDBXCallback);
end;

var
ServerMethods1: TServerMethods1;

implementation

{$R *.dfm}

function TServerMethods1.EchoString(Value: string): string;
var
param: TJSONObject;
returnresult: TJSONString;
begin
param := TJSONObject.Create(TJSONPair.Create('echostring',Value));
returnresult := pecho.Execute(param) as TJSONString;
Result := returnresult.Value;
end;

procedure TServerMethods1.reg_echo(pecho: TDBXCallback);
begin
self.pecho := pecho;
end;

end.

c++builder编写客户端代码

//---------------------------------------

#ifndef Unit4H
#define Unit4H

#include <DBXJSON.hpp>
//---------------------------------------
class TEchoCallback : TDBXCallback
{
public:
TJSONValue* __fastcall Execute(const TJSONValue* Arg);
};

#endif
//---------------------------------------


#pragma hdrstop

#include "Unit4.h"

//---------------------------------------

#pragma package(smart_init)

TJSONValue* __fastcall TEchoCallback::Execute(const TJSONValue* Arg)
{
TJSONString* returnstr;
TJSONObject* ArgObj = (TJSONObject*)Arg;
returnstr = new TJSONString(L"hello "+ArgObj->Get(0)->Value());
return returnstr;
}

自动生成的代码
#ifndef Unit3H
#define Unit3H

#include "DBXCommon.hpp"
#include "Classes.hpp"
#include "SysUtils.hpp"
#include "DB.hpp"
#include "SqlExpr.hpp"
#include "DBXDBReaders.hpp"

class TServerMethods1Client : public TObject
{
private:
TDBXConnection *FDBXConnection;
bool FInstanceOwner;
TDBXCommand *FEchoStringCommand;
TDBXCommand *Freg_echoCommand;
public:
__fastcall TServerMethods1Client::TServerMethods1Client(TDBXConnection *ADBXConnection);
__fastcall TServerMethods1Client::TServerMethods1Client(TDBXConnection *ADBXConnection, bool AInstanceOwner);
__fastcall TServerMethods1Client::~TServerMethods1Client();

System::UnicodeString __fastcall EchoString(System::UnicodeString Value);
void __fastcall reg_echo(TDBXCallback* pecho);
};

#endif

//
// Created by the DataSnap proxy generator.
//

#include "Unit3.h"

System::UnicodeString __fastcall TServerMethods1Client::EchoString(System::UnicodeString Value)
{
if (FEchoStringCommand == NULL)
{
FEchoStringCommand = FDBXConnection->CreateCommand();
FEchoStringCommand->CommandType = TDBXCommandTypes_DSServerMethod;
FEchoStringCommand->Text = "TServerMethods1.EchoString";
FEchoStringCommand->Prepare();
}
FEchoStringCommand->Parameters->Parameter[0]->Value->SetWideString(Value);
FEchoStringCommand->ExecuteUpdate();
System::UnicodeString result = FEchoStringCommand->Parameters->Parameter[1]->Value->GetWideString();
return result;
}

void __fastcall TServerMethods1Client::reg_echo(TDBXCallback* pecho)
{
if (Freg_echoCommand == NULL)
{
Freg_echoCommand = FDBXConnection->CreateCommand();
Freg_echoCommand->CommandType = TDBXCommandTypes_DSServerMethod;
Freg_echoCommand->Text = "TServerMethods1.reg_echo";
Freg_echoCommand->Prepare();
}
Freg_echoCommand->Parameters->Parameter[0]->Value->SetCallbackValue(pecho);
Freg_echoCommand->ExecuteUpdate();
}


__fastcall TServerMethods1Client::TServerMethods1Client(TDBXConnection *ADBXConnection)
{
if (ADBXConnection == NULL)
throw EInvalidOperation("Connection cannot be nil. Make sure the connection has been opened.");
FDBXConnection = ADBXConnection;
FInstanceOwner = True;
}


__fastcall TServerMethods1Client::TServerMethods1Client(TDBXConnection *ADBXConnection, bool AInstanceOwner)
{
if (ADBXConnection == NULL)
throw EInvalidOperation("Connection cannot be nil. Make sure the connection has been opened.");
FDBXConnection = ADBXConnection;
FInstanceOwner = AInstanceOwner;
}


__fastcall TServerMethods1Client::~TServerMethods1Client()
{
FreeAndNil(FEchoStringCommand);
FreeAndNil(Freg_echoCommand);
}

主窗口
//---------------------------------------

#ifndef Unit2H
#define Unit2H
//---------------------------------------
#include <Classes.hpp>
#include <Controls.hpp>
#include <StdCtrls.hpp>
#include <Forms.hpp>
#include <DB.hpp>
#include <DbxDatasnap.hpp>
#include <SqlExpr.hpp>
#include <WideStrings.hpp>

#include "Unit3.h"
#include "Unit4.h"
//---------------------------------------
class TForm2 : public TForm
{
__published:// IDE-managed Components
TSQLConnection *SQLConnection1;
TButton *Button1;
void __fastcall Button1Click(TObject *Sender);
private:// User declarations
public:// User declarations
__fastcall TForm2(TComponent* Owner);
TServerMethods1Client* Server1;
};
//---------------------------------------
extern PACKAGE TForm2 *Form2;
//---------------------------------------
#endif


#pragma hdrstop

#include "Unit2.h"
//---------------------------------------
#pragma package(smart_init)
#pragma resource "*.dfm"

TForm2 *Form2;
//---------------------------------------
__fastcall TForm2::TForm2(TComponent* Owner)
: TForm(Owner)
{
Server1 = new TServerMethods1Client(this->SQLConnection1->DBXConnection);
Server1->reg_echo((TDBXCallback*)new TEchoCallback());
}
//---------------------------------------
void __fastcall TForm2::Button1Click(TObject *Sender)
{
ShowMessage(Server1->EchoString(L"Project2"));
}
//---------------------------------------

[size=24px]远程调用EchoString时报错
Remote error: A callback parameter cannot be found at the provided index.[/size]

[解决办法]
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[解决办法]
妖哥,你试出来了吗?
我对这个问题也很想知道答案,
更希望知道为什么?