| ADO 2.5 Samples |  |
| ADO 2.5 Samples | |
This example uses the Mode property to open an exclusive connection, and the IsolationLevel property to open a transaction that is conducted in isolation of other transactions.
// BeginIsolationLevelCpp
#import "C:\Program Files\Common Files\System\ADO\msado15.dll"\
no_namespace rename("EOF","EndOfFile")
#include <ole2.h>
#include <stdio.h>
#include <conio.h>
#include "IsolationLevelX.h"
// Function Declarations
inline void TESTHR(HRESULT x) {if FAILED(x) _com_issue_error(x);};
void IsolationLevelX(void);
void PrintProviderError(_ConnectionPtr pConnection);
void PrintComError(_com_error &e);
/////////////////////////////////////////////////////////////////
// //
// //
// Main Function //
// //
// //
/////////////////////////////////////////////////////////////////
void main()
{
if(FAILED(::CoInitialize(NULL)))
return;
IsolationLevelX();
printf("Press any key to continue...");
getch();
::CoUninitialize();
}
/////////////////////////////////////////////////////////////////
// //
// IsolationLevelX() Function //
// //
/////////////////////////////////////////////////////////////////
void IsolationLevelX(void)
{
// Define ADO ObjectPointers
// Initialize Pointers on define
// These are in the ADODB :: namespace
_RecordsetPtr pRstTitles = NULL;
_ConnectionPtr pConnection = NULL;
// Define other Variables
HRESULT hr = S_OK;
IADORecordBinding *picRs = NULL; // Interface Pointer Declared
CTitleRs titlers; // C++ Class Object
LPSTR p_TempStr = NULL;
//Assign Connection String to Variable
_bstr_t strCnn("Provider='sqloledb';Data Source='MySqlServer';"
"Initial Catalog='pubs';Integrated Security='SSPI';");
try
{
// Open Connection and Titles Table
TESTHR(pConnection.CreateInstance(__uuidof(Connection)));
pConnection->Mode = adModeShareExclusive;
pConnection->IsolationLevel = adXactIsolated;
pConnection->Open(strCnn,"","",adConnectUnspecified);
TESTHR(pRstTitles.CreateInstance(__uuidof(Recordset)));
pRstTitles->CursorType = adOpenDynamic;
pRstTitles->LockType = adLockPessimistic;
pRstTitles->Open("titles",_variant_t((IDispatch*) pConnection,
true),adOpenDynamic,adLockPessimistic,adCmdTable);
pConnection->BeginTrans();
// Display Connection Mode
if(pConnection->Mode == adModeShareExclusive)
{
printf("Connection Mode Is Exclusive");
}
else
{
printf("Connection Mode Is Not Exclusive");
}
// Display Isolation Level
if(pConnection->IsolationLevel == adXactIsolated)
{
printf("\n\nTransaction is Isolated");
printf("\n\nPress any key to continue...\n\n");
getch();
}
else
{
printf("\n\nTransaction is not Isolated");
printf("\n\nPress any key to continue...\n\n");
getch();
}
// Open an IADORecordBinding interface pointer which
// we will use for binding Recordset to a class
TESTHR(pRstTitles->QueryInterface(
__uuidof(IADORecordBinding),(LPVOID*)&picRs));
// Bind the Recordset to a C++ class here
TESTHR(picRs->BindToRecordset(&titlers));
// Change the type of psychology titles.
p_TempStr = (LPSTR) malloc(sizeof(titlers.m_szau_Type));
while (!(pRstTitles->EndOfFile))
{
// Set the final character of the destination string to NULL.
p_TempStr[sizeof(titlers.m_szau_Type)-1] = '\0';
// The source string will get truncated if its length is
// longer than the length of the destination string minus one.
strncpy(p_TempStr,strtok(titlers.m_szau_Type," "),sizeof(titlers.m_szau_Type)-1);
// Compare type with psychology
if (!strcmp(p_TempStr,"psychology"))
{
// Set the final character of the destination string to NULL.
titlers.m_szau_Type[sizeof(titlers.m_szau_Type)-1] = '\0';
// Copy "self_help" title field
// The source string will get truncated if its length is
// longer than the length of the destination string minus one.
strncpy(titlers.m_szau_Type,"self_help",sizeof(titlers.m_szau_Type)-1);
picRs->Update(&titlers);
}
pRstTitles->MoveNext();
}
// Print current data in recordset.
pRstTitles->Requery(adOptionUnspecified);
// Open again IADORecordBinding interface pointer for Binding
// Recordset to a class.
TESTHR(pRstTitles->QueryInterface(
__uuidof(IADORecordBinding),(LPVOID*)&picRs));
// ReBinding the Recordset to a C++ Class
TESTHR(picRs->BindToRecordset(&titlers));
// Move to the first record of the title table
pRstTitles->MoveFirst();
//Clear the screen for the next display
system("cls");
while (!pRstTitles->EndOfFile)
{
printf("%s - %s\n",titlers.lau_TitleStatus == adFldOK ?
titlers.m_szau_Title :"<NULL>",
titlers.lau_TypeStatus == adFldOK ?
titlers.m_szau_Type :"<NULL>");
pRstTitles->MoveNext();
}
}
catch(_com_error &e)
{
// Notify the user of errors if any.
PrintProviderError(pConnection);
PrintComError(e);
}
// Clean up objects before exit.
//Release the IADORecordset Interface here
if (picRs)
picRs->Release();
if (pRstTitles)
if (pRstTitles->State == adStateOpen)
pRstTitles->Close();
if (pConnection)
if (pConnection->State == adStateOpen)
{
// Restore Original Data
pConnection->RollbackTrans();
pConnection->Close();
}
// Deallocate the memory
if (p_TempStr)
free(p_TempStr);
}
/////////////////////////////////////////////////////////////////
// //
// PrintProviderError Function //
// //
/////////////////////////////////////////////////////////////////
void PrintProviderError(_ConnectionPtr pConnection)
{
//Print Provider Errors from Connection object
//pErr is a record object in the Connection's Error collection
ErrorPtr pErr = NULL;
if((pConnection->Errors->Count)>0)
{
long nCount = pConnection->Errors->Count;
//Collection ranges from 0 to nCount-1
for(long i = 0;i < nCount;i++)
{
pErr = pConnection->Errors->GetItem(i);
printf("\t Error Number :%x \t %s",pErr->Number,
(LPCSTR) pErr->Description);
}
}
}
///////////////////////////////////////////////////////////
// //
// PrintComError Function //
// //
///////////////////////////////////////////////////////////
void PrintComError(_com_error &e)
{
_bstr_t bstrSource(e.Source());
_bstr_t bstrDescription(e.Description());
// Print Com errors.
printf("Error\n");
printf("\tCode = %08lx\n", e.Error());
printf("\tCode meaning = %s\n", e.ErrorMessage());
printf("\tSource = %s\n", (LPCSTR) bstrSource);
printf("\tDescription = %s\n", (LPCSTR) bstrDescription);
}
// EndIsolationLevelCpp
IsolationLevelX.h
// BeginIsolationLevelH
#include "icrsint.h"
//This class extracts titles and type from Title table
class CTitleRs : public CADORecordBinding
{
BEGIN_ADO_BINDING(CTitleRs)
// Column title is the 2nd field in the table
ADO_VARIABLE_LENGTH_ENTRY2(2,adVarChar,m_szau_Title,
sizeof(m_szau_Title),lau_TitleStatus,FALSE)
// Column type is the 3rd field in the table
ADO_VARIABLE_LENGTH_ENTRY2(3,adVarChar,m_szau_Type,
sizeof(m_szau_Type),lau_TypeStatus,TRUE)
END_ADO_BINDING()
public:
CHAR m_szau_Title[81];
ULONG lau_TitleStatus;
CHAR m_szau_Type[13];
ULONG lau_TypeStatus;
};
// EndIsolationLevelH
IsolationLevel Property | Mode Property