原始程序
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/*数据库管理程序*/
class EmployeeDAO{
public:
vector<EmployeeDO> GetEmployees(){
SqlConnection* connection =
new SqlConnection();
connection->ConnectionString = "...";
SqlCommand* command =
new SqlCommand();
command->CommandText="...";
command->SetConnection(connection);
SqlDataReader* reader = command->ExecuteReader();
while (reader->Read()){
}
}
};
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重构程序1
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//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;//可能传入SQL
IDBCommandFactory* dbCommandFactory;//可能传入Oracle
IDataReaderFactory* dataReaderFactory;//它们三个必须是同一系列的。所有就有了abstract factory模式
//因此需要将这三个合成同一个工厂，以保证关联性
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()){
}
}
};
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重构程序2
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//数据库访问有关的基类
class IDBConnection{
};
class IDBCommand{
};
class IDataReader{
};
class IDBFactory{
public:
virtual IDBConnection* CreateDBConnection()=0;
virtual IDBCommand* CreateDBCommand()=0;
virtual IDataReader* CreateDataReader()=0;
};
//支持SQL Server
class SqlConnection: public IDBConnection{
};
class SqlCommand: public IDBCommand{
};
class SqlDataReader: public IDataReader{
};
class SqlDBFactory:public IDBFactory{
public:
virtual IDBConnection* CreateDBConnection();
virtual IDBCommand* CreateDBCommand();
virtual IDataReader* CreateDataReader();
};
//支持Oracle
class OracleConnection: public IDBConnection{
};
class OracleCommand: public IDBCommand{
};
class OracleDataReader: public IDataReader{
};
class EmployeeDAO{
IDBFactory* dbFactory;
public:
vector<EmployeeDO> GetEmployees(){
IDBConnection* connection =
dbFactory->CreateDBConnection();
connection->ConnectionString("...");
IDBCommand* command =
dbFactory->CreateDBCommand();
command->CommandText("...");
command->SetConnection(connection); //关联性
IDBDataReader* reader = command->ExecuteReader(); //关联性
while (reader->Read()){
}
}
};
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