Java RESTful API Exercise: IOU Service

Description

Build a RESTful API service that allows users to create, read, update, and delete IOUs (I Owe You) using Java and Spring Boot.

Implement the Data Model

Inside the ious package, create an IOU entity class with the following members:

• final UUID id - unique identifier for the IOU
• String borrower - name of borrower
• String lender - name of lender
• BigDecimal amount - amount covered by IOU
• Instant dateTime - date and time of IOU being issued
• public IOU(String borrower, String lender, BigDecimal amount, Instant datetime) - constructor that should generate a new UUID, use the documentation to learn how to generate a random value.

Set the appropriate accessibility modifiers for all members and add appropriate property getters and setters.

A representative HTTP response will look something like this:

{
    "id": "5a6b7692-2322-482e-80cf-a59eedb9164f",
    "borrower": "Bob",
    "lender": "Alice",
    "amount": 1877.51,
    "date": "2023-04-23T18:25:43.511Z"
}

Implement the Repository

A repository interface, IOURepository has been provided for you. Create a class that implements this interface using a List instance as the backing store and name it something sensible, e.g. ListIOURepository, with the following members:

• final List<IOU> ious = new ArrayList<>() - list of IOUs stored in the API

Set the appropriate accessibility modifiers for all members and annotate the class as a Repository. Pay attention to the exceptions defined on the interfaces and ensure your concrete class throws as appropriate.

Implement the Service

A service interface, IOUService has been provided for you. Create a class that implements this interface using a List instance as the backing store and name it something sensible, e.g. ListIOUService, with the following members:

• final List<IOU> ious = new ArrayList<>() -
• public ListIOUService (IOURepository iouRepository)

Set the appropriate accessibility modifiers for all members and annotate the class as a Service. Ensure your code appropriately handles any exceptions thrown by the repository class.

Implement the Controller

Create an IOUController class with the following members:

• IOUService iouService - in instance of the service interface
• IOUController(IOUService iouService) - constructor that accepts an instance of the service interface

Add additional methods that defines endpoints for the following operations:

Method	URL	Description
GET	/api/ious	Get all IOUs
GET	/api/ious/{id}	Get an IOU by id
POST	/api/ious	Add an IOU
PUT	/api/ious/{id}	Replace an IOU by Id
DELETE	/api/ious/{id}	Delete an IOU by id

Set the appropriate accessibility modifiers for all members and annotate the class as a RestController.

Learning Objectives:

By the end of this exercise, you should be able to:

• Set up a Spring Boot project using a development environment
• Create a simple RESTful API for IOU tracking using controllers, services and models.
• Implement CRUD operations (Create, Read, Update, Delete) for IOUs
• Implement graceful exception handling

Getting Started

Clone the Repository

Clone this repository or or open in CodeSpaces.

git clone [REPO_URL]
cd [REPO_NAME]

Replace [REPO_URL] with the link to your GitHub repository and [REPO_NAME] with the repository's name.

Install Dependencies

Open a terminal at the root of the repo directory and run the following command to install the dependencies:

./mvnw clean dependency:resolve

If you are on a Windows machine, that will be:

mvnw clean dependency:resolve

Running the Application

To start the API from the terminal, run the following command:

./mvnw spring-boot:run

Or on Windows:

mvnw spring-boot:run

Testing the Application

You can test your endpoints using Postman or your preferred REST client.

For POST and PUT requests, you'll need to provide a request body in JSON format, e.g.:

{
  "id": "d1415cfc-dbd9-4474-94fc-52e194e384fa",
  "borrower": "John Doe",
  "lender": "Alice Smith",
  "amount": 100.0,
  "dateTime": "2023-11-02T14:30:00Z"
}

💡 Note

Remember that the id property may not be needed for all request types.