ibmdb2connection.cpp

C++连接一写常用数据库的接口

// -----------------------------------------------------------------------------
// DB2Connection::DB2Connection
// -----------------------------------------------------------------------------
DB2Connection::DB2Connection(
      int argc, 
      const char** argv)
:  
   BaseConnection(DB2_DRIVERNAME),
   _henv(SQL_NULL_HENV),
   _numHandles(0),
   _handles(NULL)
{
   // Store any arguments in a easy to use structure. (Must be even number)
   // All argument names will be in lowercase.
   
   // -- No argument processing at present
   
   
   
   // Create the DB2 environment handle
   SQLRETURN cliRC = SQL_SUCCESS;

   cliRC = SQLAllocHandle(SQL_HANDLE_ENV, SQL_NULL_HANDLE, &_henv);
   
   if (cliRC != SQL_SUCCESS)
   {
      printf("Unable to initialize DB2 environment. Is DB2INSTANCE=xxx exported correctly\n");
      throw Error("Unable to allocate DB2 Environment handle");
   }
    
   // Set attribute to enable application to run as ODBC 3.0 application 
   cliRC = SQLSetEnvAttr(_henv, SQL_ATTR_ODBC_VERSION, (void*)SQL_OV_ODBC3, 0);
} // DB2Connection::DB2Connection


// -----------------------------------------------------------------------------
// DB2Connection::~DB2Connection
// -----------------------------------------------------------------------------
DB2Connection::~DB2Connection()
{
	// Make sure we disconnect from the database.
	if (isConnected)
	{
		disconnect(120);  // 2 Minute timeout.
	}

   // Free any handles.   
   _freeCollection(CONNECTION_HANDLES);
   
   // Free the DB2 environment handle
   SQLFreeHandle(SQL_HANDLE_ENV, _henv);
} // DB2Connection::~DB2Connection


// -----------------------------------------------------------------------------
// DB2Connection::connect
// -----------------------------------------------------------------------------
void 
DB2Connection::connect(
      const string &username, 
      const string &password, 
      const string &databaseName, 
      const string &host, 
      int          maxConnections,
      int          minConnections,
      const string &optParam1,
      const string &optParam2)
{
   // Synchronize the function.
   SimpleThread_Synchronize sync(classMutex);

   // Make sure we are not already connected.
   if (isConnected)
      throw ErrorConnecting("connect(): Already connected to the database.");

   // Check and set the parameters. (Use the base class for this)
   BaseConnection::connect(username, password, databaseName, host,
      maxConnections, minConnections, optParam1, optParam2);

   // Free any handles used before.
   _freeCollection(CONNECTION_HANDLES);   
   
   // Create the collection to hold the needed handle information.
   _numHandles = maxConnections;
   _handles = (DB2Handle**)malloc(_numHandles * sizeof(DB2Handle*));
   for (int i=0; i<_numHandles; i++)
   {
      _handles[i] = new DB2Handle();
      _handles[i]->status = BaseHandle::DISCONNECTED;
   }
      
   // Connect the required specified minimum connections. The rest will be on demand.
   for (int j=0; j<minConnections; j++)
      _db2Connect(j);

   isConnected = true;      
} // DB2Connection::connect


// -----------------------------------------------------------------------------
// DB2Connection::disconnect
// -----------------------------------------------------------------------------
void
DB2Connection::disconnect(
      time_t timeout)
{
   // Synchronize the function.
   SimpleThread_Synchronize sync(classMutex);

   bool doneTimeout = false;

   // Only disconnect if we are connected.
   if (!isConnected)
      throw NotConnected("disconnect(): Not connected to the database.");
     
   // Disconnect all the open connections.
   for (int i=0; i<_numHandles; i++)
   {
      // Free the query object if it is still attached.
      // TODO

      if (_handles[i]->status == BaseHandle::CONNECTED || 
          _handles[i]->status == BaseHandle::CONNECTED_USED)
      {
         // If the handle is USED wait for the timeout.
         // Only wait once for the timeout for all connections.
         if (_handles[i]->status == BaseHandle::CONNECTED_USED && !doneTimeout)
         {
            SimpleThread::sleep(timeout * 1000);
            doneTimeout = true;
         }
            
         _db2Disconnect(i);
      }
   }
           
   isConnected = false;   
} // DB2Connection::disconnect


// -----------------------------------------------------------------------------
// DB2Connection::requestQueryConnection
// -----------------------------------------------------------------------------
void*
DB2Connection::requestQueryConnection()
{
   // This function must act as a fifo stack. The first thread in must get the first 
   //   available connection.
   // Synchronize the function.
   SimpleThread_Synchronize sync(classMutex);
   
   // Make sure we are connected.
   if (!isConnected)
      throw NotConnected("requestQueryConnection(): Not connected to the database.");
 
   // Flag that a request is occuring.
   isRequestQueryConnectionOccuring = true;

   
   // Loop until we have a valid connection or an error.
   // Built in timeout of 1 min per thread to retrieve a connection.
   int i;
   time_t now = time(NULL);
   while (time(NULL) <= now + 60)
   {
      // Try and obtain a connection
      for (i=0; i<_numHandles; i++)
      {
         // We have an available handle thats already connected.
         if (_handles[i]->status == BaseHandle::CONNECTED)
         {
            _handles[i]->queryObject = new DB2Query(this, i);
            _handles[i]->status = BaseHandle::CONNECTED_USED;

            isRequestQueryConnectionOccuring = false;
            return _handles[i]->queryObject;
         }
         
         // We have an available handle that needs to be connected.
         if (_handles[i]->status == BaseHandle::DISCONNECTED)
         {
            _db2Connect(i);
            _handles[i]->queryObject = new DB2Query(this, i);
            _handles[i]->status = BaseHandle::CONNECTED_USED;

            isRequestQueryConnectionOccuring = false;
            return _handles[i]->queryObject;
         }
      }

      // Sleep for a second to conserve resources
      SimpleThread::sleep(1000);
   }


   // If we got this far a timeout occured.
   isRequestQueryConnectionOccuring = false;
   throw QueryConnectionTimeout("requestQueryConnection(): A timout occured "
         "while trying to obtain a query connection.");
} // DB2Connection::requestQueryConnection


// -----------------------------------------------------------------------------
// DB2Connection::releaseQueryConnection
// -----------------------------------------------------------------------------
void
DB2Connection::releaseQueryConnection(
   void* queryObject)
{
   // Don't synchronize as we may need to release a connection to allow
   //  requestQueryConnection to get an available one
   
   // Find the handle that has the query connection instance
   int i;
   for (i=0; i<_numHandles; i++)
   {
      if (_handles[i]->queryObject == queryObject)
      {
         _handles[i]->queryObject = NULL;
         _handles[i]->status = BaseHandle::CONNECTED;
         
         // Check if we need to release the connection.
         // We release the connection if the connection is outside of the minimum
         // connections and there is no current request for a connection waiting.
         if (i >= minConnections && !isRequestQueryConnectionOccuring)
         {
            _db2Disconnect(i);
         }
        
         break;
      }
   }
} // DB2Connection::releaseQueryConnection