Generic Store API

The application exposes the below endpoints. Have used H2 database with some sample values loaded for the sake of simplicity.

Surge logic:

There are 3 parameters to consider:

• hit limit
• window period
• price percentage

NOTE: The above fields are configurable and can be passed while running the app. Logic:

• For an item, when the number of hits is more than the hit limit parameter in a given window period then the price of the item would be increased by price percentage
• For an item, when the number of hits is less than the hit limit parameter in a given window period, and the price has already been increase for that item, then its price will be decreased by price percentage

A couple questions to consider:

• How do we know if a user is authenticated?
  • Only when the user is authenticated a valid jwt is generated. Otherwise, the request will be rejected.
• Is it always possible to buy an item?
  • You can only view or but the item only when the user is authenticated. If required the view endpoints can be made accessible without the need to authorize.

POST /store/login

• This is the first endpoint to be invoked.
• Used Spring security for Authentication and JWT for Authorization.
• Returns a JWT which should be used to access other endpoints
• SAMPLE username/password
  • anand/anand
  • aaron/aaron
  • aidan/aaron

Request:

{
    "username":"aaron",
    "password":"aaron"
}

Sample Response:

{
    "jwt": "eyJhbGciOiJIUzI1NiJ9.eyJzdWIiOiJhbmFuZCIsImV4cCI6MTU5NTI5MDY5OCwiaWF0IjoxNTk1MjU0Njk4fQ.y6YyqE1x1f_zPGEuuJGZEFYCqtVeH1sMh2TiKTg5TJ4"
}

POST /store/register

• This endpoint can be used to register new users.
• Username already present in the database should not be registered again. (will handle this scenario in the code later)

Request:

{
    "username":"test1",
    "password":"pass1"
}

Sample Response:

User Registered successfully

GET /store/v1/items

• Returns all the items in the store.
• A valid JWT should be passed in the request header.

Sample Response:

[
    {
        "name": "Creatine",
        "description": "Naked creatine",
        "price": 10.0
    },
    {
        "name": "Protein bar",
        "description": "28gm protein bar",
        "price": 20.0
    },
    {
        "name": "Whey",
        "description": "optimum nutrition 100% Gold standard",
        "price": 30.0
    },
    {
        "name": "Casein",
        "description": "Slowly Release amino acid",
        "price": 40.0
    }
]

GET /store/v1/item/{id}

• Return the item with the id mentioned in the URL.
• A valid JWT should be passed in the request header.

Sample Response:

{
    "name": "Protein bar",
    "description": "28gm protein bar",
    "price": 20.0
}

PUT /store/v1/item/{id}/order

• Returns a one of the following message when an order is placed.
  • OUT_OF_STOCK
  • ORDER_PLACED
  • INVALID
• URL holds the item id.
• A valid JWT should be passed in the request header.

Sample Response:

ORDER_PLACED

Key features to consider

• Have externalized the key attributes i.e the surge window time, price increase percentage and hits threshold. This makes the app more flexible and configurable as per the demands.
• Have created my own fixed size CircularArrayList data structure(Unit tested). It is used to implement Surge logic rather than to clutter the DB with viewed times for each item.
• For the most parts, followed TDD approach, especially for the Surge logic
• Used Lombok to reduce boilerplate code

Testing

• Have used JUNIT 5 to implemented all the test cases
• Integration test cases alone use Springboot runner.
• Unit tests use Mockito runner. It is quick as it doesn't have to start the Spring container.
• Surefire reports can be found under the surefire-reports once you build the app

Instructions to Build

From the root folder run the below maven command to create the jar and run test cases.

mvn clean package

Instructions to Run

Using plain java -jar command.

First, change to target directory and then run the following command.

java -jar store-0.0.1-SNAPSHOT.jar

Using maven command from the root directory.

mvn spring-boot:run

The app should run in the port 8000. To change the port use the following command.

java -jar store-0.0.1-SNAPSHOT.jar --server.port=9001 

Using Docker

Command to Build:

docker build --tag store:1.0 .

Command to Run:

docker run --publish 8000:8000 --name store_container store:1.0

Improvements

• The user details to login are hard coded. The user details can be maintained in the DB. An ideal case would be to have a separate Authentication server and follow Oauth2 flow.
• Introduce API gateway (Like Spring Cloud Zuul) to intercept all the request have the Authentication and Authorization implemented there.
• Hashing(with salting) can be implemented for better protection
• Roles can be added to the Users thereby restricting access to a few endpoints for some users
• Error handling using controller advice.
• Implement shopping cart feature

Feedback

Please share your valuable feedback as that's how I learn. :)