Food Delivery Backend

@RestController
@RequestMapping("/food")
public class FoodController {
}

// 1. Restaurant Entity
import jakarta.persistence.*;

@Entity
class Restaurant {

  @Id
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  private Long id;

  private String name;
  private String location;
  private String cuisine;
}


// 2. Menu Item Entity
@Entity
class MenuItem {

  @Id
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  private Long id;

  private Long restaurantId;
  private String itemName;
  private Double price;
  private Boolean available;
}


// 3. Order Entity
@Entity
class FoodOrder {

  @Id
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  private Long id;

  private Long userId;
  private Long restaurantId;
  private Double totalAmount;
  private String status; // PLACED / PREPARING / OUT_FOR_DELIVERY / DELIVERED
}


// 4. Repository Layer
import org.springframework.data.jpa.repository.JpaRepository;

interface RestaurantRepository extends JpaRepository<Restaurant, Long> {}
interface MenuItemRepository extends JpaRepository<MenuItem, Long> {}
interface FoodOrderRepository extends JpaRepository<FoodOrder, Long> {}


// 5. Service Layer
import org.springframework.stereotype.Service;

@Service
class FoodService {

  private final RestaurantRepository restaurantRepo;
  private final MenuItemRepository menuRepo;
  private final FoodOrderRepository orderRepo;

  public FoodService(RestaurantRepository restaurantRepo, MenuItemRepository menuRepo, FoodOrderRepository orderRepo) {
    this.restaurantRepo = restaurantRepo;
    this.menuRepo = menuRepo;
    this.orderRepo = orderRepo;
  }

  public List<Restaurant> getRestaurants() {
    return restaurantRepo.findAll();
  }

  public FoodOrder placeOrder(FoodOrder order) {
    order.setStatus("PLACED");
    return orderRepo.save(order);
  }

  public FoodOrder updateStatus(Long id, String status) {
    FoodOrder order = orderRepo.findById(id).orElseThrow();
    order.setStatus(status);
    return orderRepo.save(order);
  }
}


// 6. Controller Layer
import org.springframework.web.bind.annotation.*;

@RestController
@RequestMapping("/food")
class FoodController {

  private final FoodService service;

  public FoodController(FoodService service) {
    this.service = service;
  }

  @GetMapping("/restaurants")
  public List<Restaurant> getRestaurants() {
    return service.getRestaurants();
  }

  @PostMapping("/orders")
  public FoodOrder placeOrder(@RequestBody FoodOrder order) {
    return service.placeOrder(order);
  }

  @PutMapping("/orders/{id}/status")
  public FoodOrder updateStatus(@PathVariable Long id, @RequestParam String status) {
    return service.updateStatus(id, status);
  }
}


// 7. application.properties
spring.datasource.url=jdbc:mysql://localhost:3306/food_delivery
spring.datasource.username=root
spring.datasource.password=root
spring.jpa.hibernate.ddl-auto=update


// Output:
// /food/restaurants -> List restaurants
// /food/orders -> Place order
// /food/orders/{id}/status -> Update delivery status

• 1 System to manage online food orders.
• 2 Handles restaurants and menus.
• 3 Tracks delivery status.
• 4 Built using Spring Boot.

• 1 Restaurant management
• 2 Menu management
• 3 Order processing
• 4 Delivery tracking

• 1 User selects food
• 2 Places order
• 3 Restaurant prepares food
• 4 Delivery is assigned
• 5 Order delivered

• 1 High demand real-world system
• 2 Microservices learning
• 3 Real-time processing
• 4 Scalable architecture practice

• 1 Used in apps like Swiggy and Zomato.
• 2 Used in restaurant delivery platforms.
• 3 Used in online ordering systems.
• 4 Used in cloud-based food services.
• 5 SaaS products use Food Delivery Backend using Spring Boot in services, dashboards, background jobs, and API workflows.
• 6 ERP and banking systems apply Food Delivery Backend using Spring Boot with validation, logging, review, and rollback plans.
• 7 E-commerce and healthcare platforms use Food Delivery Backend using Spring Boot carefully because reliability and data correctness matter.

• 1 A Java program first evaluates the surrounding context, then applies the Food Delivery Backend using Spring Boot rules to the current data.
• 2 The important mental model is input, transformation, result, and failure path.
• 3 In production, the same flow usually sits inside a larger layer such as a controller, service, repository, job, or UI component.

• 1 Choose the simplest implementation first, then measure real workloads.
• 2 Watch for repeated work inside loops, unnecessary allocations, and slow I/O in hot paths.
• 3 Prefer clear data structures and stable APIs before micro-optimizing syntax.

• 1 Treat external input as untrusted until it is validated.
• 2 Avoid hardcoded secrets and never print sensitive values in examples or logs.
• 3 Use established libraries for authentication, encryption, parsing, and database access.

• 1 No real-time tracking system.
• 2 Missing payment gateway integration.
• 3 Poor order status management.
• 4 Not handling peak traffic loads.
• 5 Skipping the small working example before adding framework code.
• 6 Ignoring null, empty, duplicate, and boundary inputs.
• 7 Mixing business logic, input handling, and output formatting in one place.
• 8 Using broad error handling that hides the real failure.
• 9 Forgetting to test the behavior after refactoring.
• 10 Adding clever code that future maintainers will struggle to read.

• 1 Use microservices architecture.
• 2 Integrate real-time tracking (WebSocket).
• 3 Use caching for menu data.
• 4 Secure APIs with JWT authentication.
• 5 Start with clear requirements and one minimal working example.
• 6 Use meaningful names that explain business intent.
• 7 Keep examples small enough to debug line by line.
• 8 Validate input at every trust boundary.
• 9 Handle errors explicitly and preserve useful context.
• 10 Prefer simple control flow over deeply nested logic.
• 11 Separate domain logic from I/O and framework code.
• 12 Write tests for normal, boundary, and failure cases.
• 13 Review security assumptions before production use.
• 14 Measure performance before optimizing.
• 15 Document non-obvious decisions close to the code or in project notes.
• 16 Use official documentation when behavior is version-specific.
• 17 Keep dependencies current and remove unused code.
• 18 Avoid hardcoded secrets, credentials, and environment-specific paths.
• 19 Log operational events without exposing sensitive data.
• 20 Design examples so learners can safely modify and rerun them.

• 1 Beginner: rewrite the example with different names and values.
• 2 Intermediate: add validation and handle one expected failure case.
• 3 Advanced: place Food Delivery Backend using Spring Boot inside a small service-style design with tests.

• 1 Build a small Java console feature that demonstrates Food Delivery Backend using Spring Boot.
• 2 Accept input, process it with the concept, print a clear result, and handle invalid input.
• 3 Add a README note explaining the design choice and two edge cases you tested.

• 1 If the program does not compile, check spelling, imports, braces, and file/class names first.
• 2 If output is unexpected, print intermediate values and verify each branch of the logic.
• 3 If the design feels complex, reduce it to the smallest working example and add pieces back one at a time.

• 1 Practice Food Delivery Backend using Spring Boot with a second example from a business domain such as inventory, payroll, banking, or e-commerce.
• 2 Review related Java topics that cover data flow, error handling, testing, and clean design.
• 3 Compare your solution with official documentation and simplify anything you cannot explain clearly.