private void unloadDrivers(){
		for(int i = 0; i < this.drivers.size(); ++i){
			Driver driver = this.drivers.get(i);
			try {				
				DriverManager.deregisterDriver(driver);
				System.out.println("撤销JDBC驱动程序 " + driver.getClass().getName() + "的注册");
			} catch (SQLException e) {
				System.out.println("无法撤销下列JDBC驱动程序的注册: " + driver.getClass().getName());
			}
		}
	}