Revision as of 00:16, 4 August 2010

My Project

Background

My design study is related to my part time job, where I am developing an application that can retrieve and plot data from a device that monitors air quality. The application is connected to a back end server where certain data is stored.

User operations that require communication with the server roughly include:

• Requesting help (and that the user be contacted)
• Electronically registering a device
• Calibrating a device - data about the calibration process is uploaded

Additionally, server communication is needed when the application:

• Authenticates with the server
• Pings the server to ensure network connectivity

My goal here is to create a design for the application side server interface framework. HTTPS POST requests are to be used to transfer data to the server.

Requirements

As this is a just a part of the app, the requirements are largely self imposed & generic:

• something that works
• is as nicely designed as practical
• is as easy to understand and maintain as practical
• is flexible so that new server requests can be added without much hassle

And not to forget:

• apply & learn better OO techniques

Design Study

Deliverables

• Classes that model the different request types
• Classes that allow requests to be sent over the network

Initial Design

This is my initial attempt at the design.

Design Summary

Sending Requests

Server requests are sent, and responses received using concrete insteances of IRequestSender. HttpPOSTRequestSender is the most generic concrete implementation of this interface - the two methods it has implement the actual sending/receiving mechanisms. XRequestSender is a class with a specific implementation of the IRequestSender interface for the application's purpose. It uses a composition relationship, containing an HttpPOSTRequestSender instance. Functionally, after computing and attaching a checksum to a given IRequest, the class is used to delegate Send/Receive calls to the contained HttpPOSTRequestSender.

Representing Requests

The IRequest interface is the most generic representation of a server request. In the style of HTTP POST/GET requests, a request is defined simply as something which can return a list of name-value pairs, representing the request parameters and their names (in particular a .NET 2.0 NameValueCollection).

XRequest is the abstract implementation of IRequest, implementing the shared functionality (send/get response) for all child classes. Each concrete request is then defined by a particular implementation of GetPOSTParameters() method - returning a list with different name-value parameter contents.