异步执行（通知方法）示例
本主题中的代码示例演示如何使用异步执行（通知方法）。
此函数使用异步通知打开五个连接，并在每个连接的语句上执行一个查询。
#define NUMBER_OPERATIONS 5
int AsyncNotificationSample(void)
{
RETCODE rc;
SQLHENV hEnv = NULL;
SQLHDBC arhDbc[NUMBER_OPERATIONS] = {NULL};
SQLHSTMT arhStmt[NUMBER_OPERATIONS] = {NULL};
HANDLE arhDBCEvent[NUMBER_OPERATIONS] = {NULL};
RETCODE arrcDBC[NUMBER_OPERATIONS] = {0};
HANDLE arhSTMTEvent[NUMBER_OPERATIONS] = {NULL};
RETCODE arrcSTMT[NUMBER_OPERATIONS] = {0};
rc = SQLAllocHandle(SQL_HANDLE_ENV, NULL, &hEnv);
if ( !SQL_SUCCEEDED(rc) ) goto Cleanup;
rc = SQLSetEnvAttr(hEnv,
SQL_ATTR_ODBC_VERSION,
(SQLPOINTER) SQL_OV_ODBC3_80,
SQL_IS_INTEGER);
if ( !SQL_SUCCEEDED(rc) ) goto Cleanup;
// Connection operations begin here
// Alloc NUMBER_OPERATIONS connection handles
for (int i=0; i<NUMBER_OPERATIONS; i++)
{
rc = SQLAllocHandle(SQL_HANDLE_DBC, hEnv, &arhDbc[i]);
if ( !SQL_SUCCEEDED(rc) ) goto Cleanup;
}
// Enable DBC Async on all connection handles
for (int i=0; i<NUMBER_OPERATIONS; i++)
{
rc= SQLSetConnectAttr(arhDbc[i], SQL_ATTR_ASYNC_DBC_FUNCTIONS_ENABLE, (SQLPOINTER)SQL_ASYNC_DBC_ENABLE_ON, SQL_IS_INTEGER);
if ( !SQL_SUCCEEDED(rc) ) goto Cleanup;
}
// Application must create event objects
for (int i=0; i<NUMBER_OPERATIONS; i++)
{
arhDBCEvent[i] = CreateEvent(NULL, FALSE, FALSE, NULL); // Auto-reset, initial state is not-signaled
if (!arhDBCEvent[i]) goto Cleanup;
}
// Enable notification on all connection handles
// Event
for (int i=0; i<NUMBER_OPERATIONS; i++)
{
rc= SQLSetConnectAttr(arhDbc[i], SQL_ATTR_ASYNC_DBC_EVENT, arhDBCEvent[i], SQL_IS_POINTER);
if ( !SQL_SUCCEEDED(rc) ) goto Cleanup;
}
// Initiate connect establishing
for (int i=0; i<NUMBER_OPERATIONS; i++)
{
SQLDriverConnect(arhDbc[i], NULL, (SQLTCHAR*)TEXT("Driver={ODBC Driver 11 for SQL Server};SERVER=your_server;DATABASE=your_database;UID=sa;PWD=<password>;"), SQL_NTS, NULL, 0, NULL, SQL_DRIVER_NOPROMPT);
}
// Can do some other staff before calling WaitForMultipleObjects
WaitForMultipleObjects(NUMBER_OPERATIONS, arhDBCEvent, TRUE, INFINITE); // Wait All
// Complete connect API calls
for (int i=0; i<NUMBER_OPERATIONS; i++)
{
SQLCompleteAsync(SQL_HANDLE_DBC, arhDbc[i], & arrcDBC[i]);
}
BOOL fFail = FALSE; // Whether some connection opening fails.
for (int i=0; i<NUMBER_OPERATIONS; i++)
{
if ( !SQL_SUCCEEDED(arrcDBC[i]) )
fFail = TRUE;
}
// If some SQLDriverConnect() fail, clean up.
if (fFail)
{
for (int i=0; i<NUMBER_OPERATIONS; i++)
{
if (SQL_SUCCEEDED(arrcDBC[i]) )
{
SQLDisconnect(arhDbc[i]); // This is also async
}
else
{
SetEvent(arhDBCEvent[i]); // Previous SQLDriverConnect() failed. No need to call SQLDisconnect().
}
}
WaitForMultipleObjects(NUMBER_OPERATIONS, arhDBCEvent, TRUE, INFINITE);
for (int i=0; i<NUMBER_OPERATIONS; i++)
{
if (SQL_SUCCEEDED(arrcDBC[i]) )
{
SQLCompleteAsync(SQL_HANDLE_DBC, arhDbc[i], &arrcDBC[i]);; // To Complete
}
}
goto Cleanup;
}
// Statement Operations begin here
// Alloc statement handle
for (int i=0; i<NUMBER_OPERATIONS; i++)
{
rc = SQLAllocHandle(SQL_HANDLE_STMT, arhDbc[i], &arhStmt[i]);
if ( !SQL_SUCCEEDED(rc) ) goto Cleanup;
}
// Enable STMT Async on all statement handles
for (int i=0; i<NUMBER_OPERATIONS; i++)
{
rc = SQLSetStmtAttr(arhStmt[i], SQL_ATTR_ASYNC_ENABLE, (SQLPOINTER)SQL_ASYNC_ENABLE_ON, SQL_IS_INTEGER);
if ( !SQL_SUCCEEDED(rc) ) goto Cleanup;
}
// Create event objects
for (int i=0; i<NUMBER_OPERATIONS; i++)
{
arhSTMTEvent[i] = CreateEvent(NULL, FALSE, FALSE, NULL); // Auto-reset, initial state is not-signaled
if (!arhSTMTEvent[i]) goto Cleanup;
}
// Enable notification on all statement handles
// Event
for (int i=0; i<NUMBER_OPERATIONS; i++)
{
rc= SQLSetStmtAttr(arhStmt[i], SQL_ATTR_ASYNC_STMT_EVENT, arhSTMTEvent[i], SQL_IS_POINTER);
if ( !SQL_SUCCEEDED(rc) ) goto Cleanup;
}
// Initiate SQLExecDirect() calls
for (int i=0; i<NUMBER_OPERATIONS; i++)
{
SQLExecDirect(arhStmt[i], (SQLTCHAR*)TEXT("select au_lname, au_fname from authors"), SQL_NTS);
}
// Can do some other staff before calling WaitForMultipleObjects
WaitForMultipleObjects(NUMBER_OPERATIONS, arhSTMTEvent, TRUE, INFINITE); // Wait All
// Now, call SQLCompleteAsync to complete the operation and get return code
for (int i=0; i<NUMBER_OPERATIONS; i++)
{
SQLCompleteAsync(SQL_HANDLE_STMT, arhStmt[i], &arrcSTMT[i]);
}
// Check return values
for (int i=0; i<NUMBER_OPERATIONS; i++)
{
if ( !SQL_SUCCEEDED(arrcSTMT[i]) ) goto Cleanup;
}
for (int i=0; i<NUMBER_OPERATIONS; i++)
{
//Do some binding jobs here, set SQL_ATTR_ROW_ARRAY_SIZE
}
// Now, initiate fetching
for (int i=0; i<NUMBER_OPERATIONS; i++)
{
SQLFetch(arhStmt[i]);
}
// Can do some other staff before calling WaitForMultipleObjects
WaitForMultipleObjects(NUMBER_OPERATIONS, arhSTMTEvent, TRUE, INFINITE);
// Now, to complete the operations and get return code
for (int i=0; i<NUMBER_OPERATIONS; i++)
{
SQLCompleteAsync(SQL_HANDLE_STMT, arhStmt[i], &arrcSTMT[i]);
}
// Check return code
for (int i=0; i<NUMBER_OPERATIONS; i++)
{
if ( !SQL_SUCCEEDED(arrcSTMT[i]) ) goto Cleanup;
}
// USE fetched data here!!
Cleanup:
for (int i=0; i<NUMBER_OPERATIONS; i++)
{
if (arhStmt[NUMBER_OPERATIONS])
{
SQLFreeHandle(SQL_HANDLE_STMT, arhStmt[i]);
arhStmt[i] = NULL;
}
}
for (int i=0; i<NUMBER_OPERATIONS; i++)
{
if (arhSTMTEvent[i])
{
CloseHandle(arhSTMTEvent[i]);
arhSTMTEvent[i] = NULL;
}
}
for (int i=0; i<NUMBER_OPERATIONS; i++)
{
if (arhDbc[i])
{
SQLFreeHandle(SQL_HANDLE_DBC, arhDbc[i]);
arhDbc[i] = NULL;
}
}
for (int i=0; i<NUMBER_OPERATIONS; i++)
{
if (arhDBCEvent[i])
{
CloseHandle(arhDBCEvent[i]);
arhDBCEvent[i] = NULL;
}
}
if (hEnv)
{
SQLFreeHandle(SQL_HANDLE_ENV, hEnv);
hEnv = NULL;
}
return 0;
}
此函数显示使用异步通知时同时启动多个操作并等待它们的模式：
#define ODBCVER 0x0380
#define _SQLNCLI_ODBC
// Global variables
const int g_nConnection = 700;
SQLHENV g_hEnv = NULL;
SQLHDBC g_hDbcs[g_nConnection];
HANDLE g_hevents[g_nConnection];
LONG volatile g_JobDoneNumber;
struct
{
char szOutConnectionString[500];
SQLSMALLINT iLen;
} g_connOut[g_nConnection];
void CALLBACK WaitCallBack(PTP_CALLBACK_INSTANCE Inst, PVOID Context, PTP_WAIT Wait, TP_WAIT_RESULT WaitResult)
{
UINT_PTR i = reinterpret_cast<UINT_PTR>(Context);
SQLRETURN rc ;
SQLCompleteAsync(SQL_HANDLE_DBC, g_hDbcs[(int)i], &rc);
printf("Connection %d done: RC: %d, threadid:%u \n", (int)i, rc, GetCurrentThreadId());
InterlockedIncrement(&g_JobDoneNumber);
}
int _tmain(int argc, _TCHAR* argv[])
{
for(int i = 0; i< g_nConnection; i++)
g_hevents[i] = CreateEvent(NULL, FALSE, FALSE, NULL);
PTP_WAIT waits[g_nConnection];
for(int i = 0; i < g_nConnection; i++)
{
waits[i] = CreateThreadpoolWait(&WaitCallBack, reinterpret_cast<PVOID>((UINT_PTR)i), NULL);
SetThreadpoolWait(waits[i], g_hevents[i], NULL);
}
SQLAllocHandle(SQL_HANDLE_ENV, SQL_NULL_HANDLE,&g_hEnv);
SQLSetEnvAttr(g_hEnv,SQL_ATTR_ODBC_VERSION, (SQLPOINTER)SQL_OV_ODBC3_80, SQL_IS_UINTEGER);
for(int i = 0; i < g_nConnection; i++)
{
SQLAllocHandle( SQL_HANDLE_DBC, g_hEnv , &g_hDbcs[i]);
SQLSetConnectAttr(
g_hDbcs[i],
SQL_ATTR_ASYNC_DBC_FUNCTIONS_ENABLE,
(SQLPOINTER)SQL_ASYNC_ENABLE_ON,
SQL_IS_INTEGER);
SQLSetConnectAttr(g_hDbcs[i], SQL_ATTR_ASYNC_DBC_EVENT, g_hevents[i], SQL_IS_POINTER);
}
// make connections
g_JobDoneNumber = 0;
for(int i = 0; i < g_nConnection; i++)
{
SQLDriverConnect(g_hDbcs[i],NULL,
(SQLCHAR*)"DRIVER={ODBC Driver 18 for SQL Server};Server=your_server;Encrypt=yes;database=your_database;uid=usr;pwd=<password>",
SQL_NTS, (SQLCHAR*)g_connOut[i].szOutConnectionString, 500, &g_connOut[i].iLen, SQL_DRIVER_NOPROMPT);
}
printf("connect wait..\n");
while(g_JobDoneNumber < g_nConnection)
SleepEx(50, false);
// disconnect
for(int i = 0; i < g_nConnection; i++)
SetThreadpoolWait(waits[i], g_hevents[i], NULL);
printf("disconnect wait..\n");
g_JobDoneNumber = 0;
for(int i = 0; i < g_nConnection; i++)
SQLDisconnect(g_hDbcs[i]);
while(g_JobDoneNumber < g_nConnection)
SleepEx(50, false);
for(int i = 0; i < g_nConnection; i++)
CloseThreadpoolWait(waits[i]);
for(int i = 0; i < g_nConnection; i++)
{
CloseHandle(g_hevents[i]);
SQLFreeHandle(SQL_HANDLE_DBC, g_hDbcs[i]);
}
SQLFreeHandle(SQL_HANDLE_ENV, g_hEnv);
return 0;
}