7 Essential Spring Boot 3 Practices Every Backend Developer Should Know

Introduction

This article examines seven easily overlooked details in Spring Boot 3 development that can cause traps, aiming to improve code quality, testability and maintainability.

Key Points

2.1 Avoid field injection with @Autowired/@Resource

Field injection creates tight coupling and hampers testing. Prefer constructor injection, optionally using Lombok's @RequiredArgsConstructor. Example:

private final UserRepository userRepository;

public UserService(UserRepository userRepository) {
    this.userRepository = userRepository;
}

Lombok is discouraged in this guide.

2.2 Keep business logic out of controllers

Controllers should only handle HTTP requests and delegate business logic to service layers, which simplifies unit testing and promotes reuse.

@RestController
@RequestMapping("/products")
public class ProductController {
    private final ProductService productService;
    public ProductController(ProductService productService) {
        this.productService = productService;
    }

    @GetMapping("/{id}")
    public ResponseEntity<Product> getProduct(@PathVariable Long id) {
        Product product = productService.getProductById(id);
        return ResponseEntity.ok(product);
    }
}

2.3 Replace @Value with @ConfigurationProperties

@Value lacks structure and spreads configuration throughout the code. Define a dedicated configuration class annotated with @ConfigurationProperties to bind related properties.

@ConfigurationProperties(prefix = "pack.app")
public class AppConfig {
    private String title;
    private String version;
    private Integer uid;
    // getters and setters
}

2.4 Keep constructors simple

Move heavy initialization out of constructors, using @PostConstruct methods or factory patterns.

public class CommonComponent {
    private final CommonService commonService;

    public CommonComponent(CommonService commonService) {
        this.commonService = commonService;
    }

    @PostConstruct
    public void init() {
        // TODO
    }
}

2.5 Use separate configuration files for different environments

Define application-{profile}.properties or .yml files and activate the appropriate profile.

spring:
  profiles:
    active:
      - dev

2.6 Prefer exceptions over return‑value error codes

Throw a specific exception instead of returning an error wrapper, and handle it globally with @RestControllerAdvice.

@Service
public class ProductService {
    private final ProductRepository productRepository;
    public ProductService(ProductRepository productRepository) {
        this.productRepository = productRepository;
    }

    public Product queryById(Long id) {
        return productRepository.findById(id)
            .orElseThrow(() -> new ProductNotFoundException("Product not found, id: " + id));
    }
}

2.7 Use ResponseEntity as the response type

ResponseEntity provides flexible control over status codes, headers and body, and supports generics. When custom response objects are needed, they can still be used.