Project assignment 3: implementing shopping cart via servlets

Due Friday, April 5th at 6pm in Elena's office

See the submission instructions.

Intermediate report: On Tuesday, April 2nd, before 1:30pm, please submit a short note with your solution for part 1 and with (at least partial) solution for part 2. You may change your decisions later, only the last submission will be graded. You can send me this part by e-mail (cc all project members) or as a brief paper note in class.

In this part of the project you will write servlets which implement a shopping cart for your web site. The web site will keep track of user's requests via a session. You will also implement cookies to identify the user (or, rather, the browser) even if the session has terminated.

Instructions on how to compile and run your servlets


Do not use System.exit() anywhere in your servlets. This will shut down TOMCAT (the progranm that runs servlets on birch) and you will not be able to run any servlets until it's restarted!

Please keep in mind that this project requires more communication between project group members than the previous ones. You cannot just divide up the work and each do a separate part, because the programming decisions that you make for one part affect the implementation of another.

Your best strategy is to start on the project all together, and once you have figured out and tested the things that you all will be using, such as session attributes, you can each work on details of a particular part of the assignment. When the work is mostly finished, you need to get together again to test your site and make sure that information is passed correctly between all the servlets.

Part 1: mapping out your site

Your site will contain several servlets. In particular, you may have an entry servlet, several product categories, pages with extra information, and so on. You will also have a few pages related to a shopping cart, at least a page that displays the selected products, the page to identify the user, and the "Thank you" page.

Please read the entire assignment carefully and write down the names and description of all the servlets that you need to write. Agree on the names so that you can use them in forms (to indicate which servlet will be handling a POST request or to make an HTTP reference to another servlet). Agree on which servlet will be doing what. You may change your decisions later, but it's important to write them down carefully.

Each group will be using a separate web application (a package of servlets, images, .jar files and so on), so you don't need to worry about naming your servlets differently from another group. All your servlet classes will be in the same directory, so you can refer to them just by name without the path.

Appearance of the web site

You don't need to worry too much about the page appearance, but some style decisions might be helpful. You might want to choose background color or image, color of links and text, and the icons that you are using for the shopping cart and other buttons. There are web sites where you can download graphics for free. Make sure that you are not copying anything that's copyrighted. The only image formats that you should use are .gif and .jpg. The images must be stored in the directory "images" of your web application.

It is important to agree on the style early on, so that all your servlets have similar appearance. For instance, the link to a shopping cart may appear in the right upper corner on every page. If one page uses icon for the link, then all pages should use the same icon.

Part 2: implementing session attributes

A session contains attributes that store information about the user's selections. The session is shared between servlets on the same server. A servlet finds out the stored information by retrieving an attribute using the getAttribute() method of a session.

Your task in this part is to decide what attribute(s) you will need to to be able to pass the information. The information will include the list of products that the user has selected, the attributes of these products (such as size, color, etc.), and possibly the quantity.

You may also implement a wish list: products that the user selects, but does not buy at the checkout.

You need to write a class or classes which implement the session attributes. Think of methods that you will need to work easily with the attribute: adding products to the cart, deleting products, modifying products, check for repetitions, and so on. In the example in class (the ice cream shop) there is a class Order, but the attribute of session is a vector of Orders, which was handled explicitly in the doGet() method. In larger programs it would be more convenient to add an extra class for handling the vector itself.

I strongly recommend that you:

Part 3: displaying a clickable list of products

In this part you will need to generate a page, or pages, of products offered by your web site. Since product information is stored in the database, and may change, the pages for the products must be generated by getting the product information from the database and creating an HTML page with a button for each product. When the user clicks on the button, the product should be added to the list of user's choices stored as an attribute of a session.

More precisely, the doGet() method of a servlet that displays products should do the following:

  1. Get the session object, get the writer for writing the response. If the session object does not exist, a new session has to be created.
  2. Connect to the database using JDBC package (as in the previous assignment).
  3. Get the list of products for the page by running an SQL query.
  4. Generate a page which contains forms (as in the Ice Cream Shop example in class), one for each product in the result set, possibly with some additional options (s.a. size, color, quantity, etc.).
  5. If the doGet() method is invoked from a post method and the user has added a product to the shopping cart, then add the product to the cart (by modifying the session's attribute containing the list of products).
The doPost() method of the servlet should do the following:
  1. Retrieve the parameter of the form. Add the product to the shopping cart (a particular product is identified by a hidden attribute of the form). If the user has selected some options for the product, the options should be indicated in the shopping cart entry as well.
  2. Call the doPost() method.
In addition to the product pages, it might be a good idea to have a separate entrance page for the web site with the site's name, logo, etc.. If you don't have such a page, then indicate which of the product pages is the entrance page.

Part 4. Displaying the shopping cart.

When user clicks on the shopping cart icon (or on the link, depending on your implementation), the control goes to the servlet which does the following:
  1. Displays the list of products in the shopping cart with the chosen options (if any) and the prices, with the total shown after the list. The prices should be retrived from the database, since you need to get the most recent price. The list should be displayed as a form which allows user to change the quantity and possibly the options. The list also should give user an option of deleting a product from the cart. When the user modifies the selection and clicks on a button (say, "Modify"), the cart gets redisplayed with the new selection.
  2. In addition to the list of products, the cart should offer the following options:
The checkout includes two servlets:
  1. a form where the user enters their name. No credit card number or other information is needed, since this has been done in the order form. Even though the applets are not yet part of the site, we will try to integrate them into the web site later. After the user enters the name, the "Thank you" page is displayed.
  2. "Thank you" page has (approximately) the following text:
    Dear the name entered in the previous page!

    Thank you for buying the list of products
    We have more great products at our web site.
    Please click here to continue shopping or come back to our site again soon!

    At this point the session should be invalidated.

Part 5. Invalidating the session

The option of deleting all products from a shopping cart should be given at least by the servlet that displays the shopping cart, but possibly by other pages as well.

When the user selects this option, the session is invalidated, i.e. all the attributes are erased. You use the method invalidate() of class HttpSession to implement this.

Make sure that when the session is invalidated, no information from the previous session is stored.

Part 6. Identifying user by a long-term cookie

Important: the name of the cookie MUST include the name of your project, s.a. myproject.usercookie. Otherwise servlets sent to a browser by one project group may intefere with cookies sent by another. Session cookies automatically include the path to the servlet into their name, but your "hand-made" cookies don't!

In addition to the cookies that manage the session (which by default exist for a half-an-hour after the session is finished), you need to identify the user by a cookie that has a longer life time. In particular, you need to do the following:

  1. If the session is new, check if the user's browser has a cookie from your site stored in the browser. If yes, then check out the cookie's the name or user ID stored in the cookie.

    In real life you might use this information to customize the web site according to the user's preferences, to display advertisements tailored to choices of the user, or to keep statistics. In this simple simluation just greet the user by name if the cookie stores a name, or display the greeting "Welcome back!" if it doesn't. Optionally, you might display the product web page that the user has visited last.

    If the user does not have a cookie, send a cookie to the browser with some randomly generated ID. The life time of the cookie should be 1 month (in real life it would be longer, but in our case there is no point of keeping it longer than that).

  2. On the pages when the user enters their name (such as the checkout page) you need to retrieve the cookie, store the name of the user, and send the cookie back to the user.
  3. You should give the user an option of deleting the cookie (s.a. "If you don't want us to remember your name, please click here"). This message should be displayed in the "Thank you" page. If the user clicks on the link, the cookie gets deleted.
The age of a cookie is set by a setMaxAge(int n) method. The age is set in seconds. setMaxAge(0) deletes the cookie.

Part 7. Testing your servlets

For all parts of the assignment please make sure to test your servlets thoroughly. When you submit the assignment, please describe all the tests that you performed, the results, and your conclusions. The grade for this part is a large part of the total assignment grade!

In addition to testing your servlets as you are writing them, you might want to test each other's work when it's in a fairly completed state.

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Spring Semester 2002