Spring Boot - n-Tier Architecture - 🧪 Guided Exercise: BurgerByte v2 – Refactor for Scalability

[akash-coded]

🧪 Guided Exercise: BurgerByte v2 – Refactor for Scalability

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🧠 Core Learning Objectives:

• Realize why the Service Layer is needed, not just how
• Learn to decouple business logic from controllers
• Practice CRUD using in-memory data (Java Collections)
• Reinforce clean code, single responsibility principle (SRP)
• Begin writing testable, maintainable code

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🧩 Phase 1: Quick & Dirty API (Just Controller + Model)

Ask them to create this ‘naive’ version that handles everything inside the controller.

🍔 The Feature:

• Model: Burger

• Controller: BurgerController

• CRUD endpoints:

  • GET /api/burgers → list all
  • POST /api/burgers → add new
  • GET /api/burgers?id=1 → get one
  • DELETE /api/burgers?id=1 → delete one

Use an internal List<Burger> inside the controller.

Let them build it. Let them feel the clutter.

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🤯 Discussion Prompt:

After they build it:

🗣 “What if we need to reuse this burger-fetching logic in another controller?”
🗣 “How do we unit test the logic without spinning up Spring Boot?”
🗣 “What if we now add multiple resources (Drinks, Combos)? Will we copy-paste logic?”
🗣 “What if the logic for computing price gets longer?”
🗣 “What if a new developer has to debug your controller?”

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🛠 Phase 2: Refactor Using a BurgerService

Now guide them to extract all business logic into a separate service class.

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✅ Folder Structure (explain it)

com.burgerbyte
├── controller
│   └── BurgerController.java
├── model
│   └── Burger.java
├── service
│   └── BurgerService.java
└── RateburgerApplication.java

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🧱 Model Class

public class Burger {
    private int id;
    private String name;
    private double price;

    // Getters, Setters, Constructors
}

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🧠 Phase-2 Starter Task

Split logic:

• BurgerService manages the List<Burger> and all add/delete/get/search logic
• BurgerController just routes to the service

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💡 Provide Partial Templates

🔧 BurgerService.java (fill in the blanks)

@Service
public class BurgerService {

    private List<Burger> burgerList = new ArrayList<>();

    // TODO: Add burger to list
    public void addBurger(Burger burger) {
        // Implement logic
    }

    // TODO: Return full list
    public List<Burger> getAll() {
        return null; // Replace with actual
    }

    // TODO: Find by ID
    public Burger getById(int id) {
        // Use stream().filter().findFirst()
        return null;
    }

    // TODO: Delete burger
    public boolean deleteById(int id) {
        // Find and remove from list
        return false;
    }
}

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🕹️ BurgerController.java

@RestController
@RequestMapping("/api/burgers")
public class BurgerController {

    @Autowired
    private BurgerService burgerService;

    @PostMapping
    public String addBurger(@RequestBody Burger burger) {
        burgerService.addBurger(burger);
        return "Burger added!";
    }

    @GetMapping
    public List<Burger> getAll() {
        return burgerService.getAll();
    }

    @GetMapping(params = "id")
    public Burger getById(@RequestParam int id) {
        return burgerService.getById(id);
    }

    @DeleteMapping
    public String delete(@RequestParam int id) {
        boolean deleted = burgerService.deleteById(id);
        return deleted ? "Deleted!" : "Not Found!";
    }
}

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🧠 Developer Nugget: WHY Service Layer?

1. 🧹 Separation of Concerns
   Keep controller thin. Avoid bloated @RestControllers.

2. 🔁 Reusability
   Other controllers or scheduled jobs can reuse BurgerService.

3. 🧪 Testability
   Easily mock BurgerService for unit testing.

4. 🔄 Pluggability
   In future, we’ll plug JPA repository instead of in-memory list without touching controller.

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🧪 Bonus Challenge: Add Business Logic in Service

• Add a rule: if burger.price < 50, reject burger as "Too cheap for Mars!"
• Add a method getAffordableBurgers(double maxPrice)
• Add search: /api/burgers/search?name=cheez (partial match)

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🧾 Deliverables

• Burger.java (Model)

• BurgerController.java (Routing only)

• BurgerService.java (All logic)

• Postman screenshots

• Answer the question:

  "What problem did the service class solve for you as a developer?"

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🧠 Reflection Prompt

Ask each student:
“What’s one benefit of having a service layer you experienced personally while building this?”

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📦 Optional Extension (if time permits)

• Add a new model: Drink
• Create a parallel controller + service for DrinkService
• See how logic gets reused across resources

[Sdey0907]

**

Task- BurgerByte -v2_n-Tier Architecture_Spring Boot_Sayan Dey_Completed

**

BurgerByteAPI_V2_SpringBoot.zip

[prasetha21-max]

PRASETHA N
rateburger.zip

[vbhavana1]

RateBurger_Spring.zip