You can use a parallel port easily. For the keypad part, use an Intel 8279 – it’s a keyboard controller. (It’s old technology – circa 1978 – but it’s still the easiest way to interface a keypad.)

For the sensor, hang a 1k resistor on the 5 volt line and connect the sensor between the other end of the resistor and ground. Connect the junction of the sensor and the resistor to a pin on a parallel port. (I’d use an isolation resistor and a buffer chip to keep transients from blowing the port.) Then you watch for a transition on that port pin – whether it goes from 0 to 1 or 1 to 0 depends on whether the sensor is open or closed when the door is closed. They come either way.

Wouldn’t it be simpler with USB.
You can much easily find components for usb and it is easier to program.