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CSE3OAD Assignment 2 
Due Date: 5 June 2020, Friday, 10:00 AM 
 
Assessment: This assignment 2 is worth 30% of the final mark for CSE3OAD. 
This is an individual assignment. 
Copying, Plagiarism: Plagiarism is the submission of somebody else’s work in a 
manner that gives the impression that the work is your own. The Department 
of Computer Science and Information Technology treats plagiarism very 
seriously. When it is detected, penalties are strictly imposed. Students are 
referred to the Department of Computer Science and Information 
Technology’s Handbook and policy documents with regard to plagiarism. 
No extensions will be given: Penalties are applied to late assignments (5% of 
your total assignment mark given is deducted per day, accepted up to 5 days 
after the due date only). If there are circumstances that prevent the 
assignment being submitted on time, an application for special consideration 
may be made. 
See the departmental Student Handbook for details. Note that delays caused 
by computer downtime cannot be accepted as a valid reason for a late 
submission without penalty. Students must plan their work to allow 
for both scheduled and unscheduled downtime. Assignments submitted more 
than 5 days late will receive the mark of 0. 
Return of Assignments: Students are referred to the departmental Student 
Handbook for details. 
Objectives: To design and implement a RESTful API that will provide an access 
endpoint to a data source controller similar to the one you implemented using 
JDBC in Assignment 1. 
 
Introduction 
 
The aims of the assignment are: 
• To implement web services for making available resources regarding 
your fridge groceries and items. The groceries and items are those that 
you have worked with in Assignment 1. 
o Using Java Reflection and Servlet API 
• To apply the relevant validation strategies to the grocery, using the 
Validation Framework we built 
in Lab 07. 
 
 
Files Provided: 
 
The following are provided in the fridge directory (zip file) 
 
• The servlet descriptor file web.xml (directory fridge/WEB-INF) 
• The jar files for JSON conversion and JDBC (MySQL) driver (directory 
fridge/WEB-INF/lib) 
• The following in the directory fridge/WEB-INF/classes 
o The Java files for the Validation framework (complete files): 
▪ Min.java, MinValidator.java 
▪ Max.java, MaValidator.java 
▪ NotNull.java, NotNullValidator.java 
▪ CharCount.java, CharCountValidator.java 
▪ Validator.java, ValidationException.java 
o The Data Source Controller, FridgeDSC.java 
▪ Grocery.java (excluding the validation annotations required for task XXX) 
▪ Item.java 
o The Controllers (incomplete) 
▪ GroceryController.java 
▪ ItemController.java 
o The Router Servlet (incomplete) 
▪ FridgeRouterServlet.java 
o A few custom Exception sub-classes to be used throughout this Assignment 2 
(complete) 
▪ MissingArgumentException.java 
▪ ResourceNotFoundException.java 
▪ UpdateNotAllowedException.java 
 
• The SQL Script to create and populate your database 
 
o CreateDatabaseScript.sql 
 
Task 1 - Optional 
 
1. Study the Validation Framework provided (complete code provided) as well 
as the lecture and lab materials that covered Java Reflection, Annotations and 
the Validation Framework. 
 
2. TODO: Clearly annotate the relevant fields of the Grocery.java model. 
o You may want to test if your validation on the model is working (see how we 
did that in the labs) – a static main has been provided in Grocery.java for you 
to add your testing code. 
 
Task 2 
 
The controllers are the bridge between the FridgeDSC class and the 
FridgeRouterServlet class. 
 
• Study the complete FridgeDSC.java file provided, paying attention to 
its constructor (some changes have been made, which differs from 
Assignment 1) 
o NOTE: the constructor requires database host, username and 
password as arguments For each controller (GroceryController.java and 
ItemController.java) 
 
• TODO: Complete each of the method stubs provided. Each method 
stubs needs to make a call to a relevant FridgeDSC.java method. Identify 
which one and code it in the controllers. 
o You may want to test if the controllers are responding properly when 
calling each FridgeDSC method – a static main method has been 
provided in each class for you to add your testing code. 
 
Task 3 
 
Implement the servlet (FridgeRouterServlet class) - The purpose of this servlet 
class is to: 
 
1. Identify which resource the URL is requesting, using HttpServletRequest 
• example, the resource from a browser call to 
http://localhost:8080/fridge/api/grocery 
will then be “grocery” (the same applies for a call to 
http://localhost:8080/fridge/api/GroCerY) 
• the HTTP method can also be found here (in this example, a browser 
call means using HTTP GET method) 
 
2. Using the Servlet API, 
• retrieve your database host, username and password from the servlet 
descriptor file web.xml. (add your MySQL username password where 
needed in file web.xml) 
 
3. Using the Reflection API, 
a. Find if the resource controller exists - from the above example, 
resource “grocery” should have a matching controller class 
GroceryController [hint: using Class.forName(…)] 
b. Create an instance of such controller class 
NOTE: 
• HTTP GET (with no parameters identified) maps to controller method 
get() 
• HTTP GET (with parameter identified) maps to controller method 
get(id) 
• HTTP POST (with parameter identified) maps to controller method 
add(…) 
• HTTP PUT (with parameter identified) maps to controller method 
update(id) 
• HTTP DELETE (with parameter identified) maps to controller method 
delete(id) 
 
c. If we have an HTTP GET method, with no identifiable parameters (from the 
above example), find if GroceryController class has a no-argument method 
named get() 
• then, make a call to this method, and store the returned data 
 
d. Do the same (a, b, c above) if the resource identified is “item” 
• NOTE: clearly distinguish the difference between controller classes 
GroceryController and ItemController 
 
4. Using the Gson package provided and HttpServletResponse 
a. Convert any returned data (from controller method call) to JSON data 
(using Gson) 
b. Convert any valid case messages (if any) to JSON data (using Gson) 
c. Send the any JSON data back to the 
d. Making sure any potential errors (throughout steps 1-4 
described for this Task 3) are caught, identified and send back to 
the browser (using GSON to convert messages to JSON) and using 
appropriate HTTP Status Codes and adequate (descriptive) error 
messages. 
 
You will use Postman to test your API (https://www.getpostman.com/) – More 
on Postman will be covered in your lab sessions. 
 
Testing your API (Using Postman) 
 
The resources to access (using Postman for example) for the assignment 2 are: 
• http://localhost:8080/fridge/api/grocery 
on the above you can 
▪ get all (GET http method with the above URL) 
▪ get one (GET http method with id 10: 
http://localhost:8080/fridge/api/grocery/10 ) 
▪ add one (POST http method with above URL, with additional grocery info in 
JSON format sent as POST data) 
▪ delete one (DELETE http method with id 11: 
http://localhost:8080/fridge/api/grocery/11) 
▪ update one (PUT http method with id 9: 
http://localhost:8080/fridge/api/grocery/9) 
• http://localhost:8080/fridge/api/item 
▪ get all items (GET http method with the above url) 
 
NOTE: 
 
The update grocery requirement is different from usual updates (only one field 
is updated, that is, reduced by 1) - so the PUT method does not contain any 
data. and the action of reducing grocery quantity is done on the grocery found 
(if any) by the provided id the id (10, 11, 9) provided above are examples - 
groceries with those id should exist in your database for the relevant action to 
be possible. (Else it should return a well-defined and meaningful error 
message) 
 
What to submit 
 
Electronic copy of all of the classes required to run the application, including 
those that are provided, are to be submitted to LMS. 
The only requirement is that your program should work on the database tables 
grocery and item which must have the same structure as the one in the 
provided MySQL script (CreateDatabaseScript.sql ) 
 
For each class that you submit, you must include, as part of the comments, at 
the beginning of each file, 
 
o your full name (with surname in capital), 
o your student ID, 
o your username (if different from student ID), and 
o the subject code (CSE3OAD) 
 
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