//数据库访问有关的基类

class IDBConnection{

};

class IDBConnectionFactory{

public:

virtual IDBConnection* CreateDBConnection()=0;

};

class IDBCommand{

};

class IDBCommandFactory{

public:

virtual IDBCommand* CreateDBCommand()=0;

};

class IDataReader{

};

class IDataReaderFactory{

public:

virtual IDataReader* CreateDataReader()=0;

};

//支持SQL Server

class SqlConnection: public IDBConnection{

};

class SqlConnectionFactory:public IDBConnectionFactory{

};

class SqlCommand: public IDBCommand{

};

class SqlCommandFactory:public IDBCommandFactory{

};

class SqlDataReader: public IDataReader{

};

class SqlDataReaderFactory:public IDataReaderFactory{

};

//支持Oracle

class OracleConnection: public IDBConnection{

};

class OracleCommand: public IDBCommand{

};

class OracleDataReader: public IDataReader{

};

class EmployeeDAO{

IDBConnectionFactory* dbConnectionFactory;

IDBCommandFactory* dbCommandFactory;

IDataReaderFactory* dataReaderFactory;

public:

vector<EmployeeDO> GetEmployees(){

IDBConnection* connection =

dbConnectionFactory->CreateDBConnection();

connection->ConnectionString("...");

IDBCommand* command =

dbCommandFactory->CreateDBCommand();

command->CommandText("...");

command->SetConnection(connection); //关联性

IDBDataReader* reader = command->ExecuteReader(); //关联性

while (reader->Read()){

}

}

};