15.1.1- A Web-based Classifieds System

A Web-based Classifieds System

We'll implement a web-based classified ad system. Any user who us trying to buy an item can:

• View items for sale
• Bid on an item they wish to purchase

In addition, any user who is trying to sell an item can:

• Place a new item for sale
• Browse a list of the items that they're trying to sell, and examine the bids that have been made on each of those items
• Accept a bid on an item that they're selling

This system will also allow users to do straightforward administrative tasks like:

• Browse the listings to see what's for sale
• Register with the system (users can browse without registering; but they must register if they want to sell an item or bid for an item)
• Log on to the system
• Change their registration details

If our web site takes off, we'll have a large user-base – some will be buyers and some will be sellers (and hopefully some will do some buying and some selling via our system). In addition, some users will be unregistered 'window-shoppers' – these users will need to register when they spot something they want to bid for.

The Advantages over a Print-based Classifieds System

Our Internet-based classified ad system provides certain advantages to the seller over traditional printed classifieds:

• When a seller submits an item for sale, it's immediately viewable by potential buyers. There's no time delay while we all wait for the newspaper to be printed
• Responses from potential buyers are held by the system's data store – rather than being passed directly back to the seller. This means that the seller doesn't have to be available to respond 24 hours a day
• The seller can dynamically adjust the price – based on the amount of response an item receives

The Internet classified ad system also provides advantages for potential buyers:

• Shoppers can see the level of interest in an item before determining the price they are willing to pay
• When a shopper makes a bid, he is told whether the bid is the highest bid made on that item
• The global nature of the Internet means that the potential audience for each advert is global – it's not limited to the encatchment area of a printed newspaper

Building the Application

We'll build our application in stages. Each stage will build on the previous stages, and will add a new piece of functionality to the application. The sequence we'll follow in this chapter is:

• Database setup
• Home page construction
• User registration and login
• Adding items to the sale listings
• Browsing the listings and bidding for items
• Accepting a bid and completing the sale

To get us started, let's take a look at the ASP pages that will feature in our application. There are 14 pages altogether. Each of these pages serves a different function and contains the code for carrying or certain tasks. The pages are given names that reflect their functionality:

When we consider any application of this size, we can gain a lot of understanding by representing the relationship between pages in a graphical way. As you work through the application, you may find the following diagram useful – it shows the routes that we'd expect our users to travel as they use the application:

The click-throughs and redirections shown in this diagram illustrate the key stages of the sale process. As you'll see when we come to write the code, there are other click-throughs which are not shown in this diagram. These additional links give users the option of moving directly to pages like Login.asp, Register.asp and BrowseListings.asp – thus allowing the user a controlled amount of extra freedom to move between the pages of the application.