Product Inventory REST API

Problem Context

You are building a backend service for an e-commerce platform. Your task is to design and implement a Spring Boot REST endpoint that manages product inventory. The endpoint must handle creating and retrieving products with proper validation, exception handling, and structured logging.

Task

Given a JSON payload representing a product creation request, simulate what your Spring Boot REST endpoint would return — including proper HTTP status codes, validation error messages, and structured response bodies.

Your solution should model the behavior of:

• POST /api/v1/products — Create a new product
• GET /api/v1/products/{id} — Retrieve a product by ID

Input/Output Format

Input: A JSON string representing either a product creation request or a retrieval query.

For creation, the payload includes:

• name (string, required, 2–100 chars)
• price (number, required, > 0)
• quantity (integer, required, >= 0)
• category (string, required, one of: ELECTRONICS, CLOTHING, FOOD)

For retrieval, the payload is: {"action": "GET", "id": <number>}

Output: A JSON string representing the HTTP response body and status code in format: {"status": <code>, "body": <object>}

Examples

Example 1 — Successful Creation:

Input:  {"action": "POST", "name": "Laptop", "price": 999.99, "quantity": 50, "category": "ELECTRONICS"}
Output: {"status": 201, "body": {"id": 1, "name": "Laptop", "price": 999.99, "quantity": 50, "category": "ELECTRONICS"}}

Explanation: All fields are valid. The endpoint creates the product and returns HTTP 201 Created with the persisted product (including generated ID).

Example 2 — Validation Failure:

Input:  {"action": "POST", "name": "A", "price": -5.0, "quantity": 10, "category": "ELECTRONICS"}
Output: {"status": 400, "body": {"errors": ["name must be between 2 and 100 characters", "price must be greater than 0"]}}

Explanation: name is too short and price is negative. The @Valid annotation triggers MethodArgumentNotValidException, returning HTTP 400 with descriptive field errors.

Example 3 — Resource Not Found:

Input:  {"action": "GET", "id": 999}
Output: {"status": 404, "body": {"error": "Product with id 999 not found"}}

Explanation: No product exists with ID 999. A custom ResourceNotFoundException is thrown and handled by , returning HTTP 404.