Common Mistakes in Spring Boot Development (and How to Avoid Them)

Spring Boot simplifies many aspects of building applications, but there are several pitfalls that developers often fall into. In this post, we’ll explore common mistakes in Spring Boot development and provide detailed examples on how to address them.

1. Not Understanding Lazy vs. Eager Loading

• Mistake: Using eager loading without need can load unnecessary data, hurting performance.
• Example: Suppose you have a User entity that references a Profile entity. By default, JPA uses lazy loading for the Profile association, meaning the Profile data will only be fetched when explicitly called. However, developers sometimes switch to eager loading unnecessarily, which could lead to N+1 query issues.
• Solution: Stick with lazy loading where possible and only use eager loading when it makes sense.

@ManyToOne(fetch = FetchType.LAZY)
private Profile profile;

2. Improper Exception Handling

• Mistake: Sending cryptic error messages to users and not providing centralized error handling can confuse users and make debugging difficult.
• Solution: Use @ControllerAdvice and @ExceptionHandler to create centralized exception management.
• Example:

@ControllerAdvice
public class GlobalExceptionHandler {
    @ExceptionHandler(Exception.class)
    public ResponseEntity<String> handleException(Exception e) {
        return new ResponseEntity<>("Custom error message", HttpStatus.INTERNAL_SERVER_ERROR);
    }
}

3. Hardcoding Configuration Values

• Mistake: Hardcoding values like database credentials directly in the code.
• Solution: Use Spring’s externalized configuration with properties or environment variables.
• Example: Place sensitive values in application.properties or use environment variables

spring.datasource.url=${DB_URL}
spring.datasource.username=${DB_USER}
spring.datasource.password=${DB_PASSWORD}

4. Overusing @Autowired

• Mistake: Relying too heavily on @Autowired for field injection, which makes the code hard to test and maintain.
• Solution: Use constructor injection for better readability and easier testing.
• Example:

@Service
public class UserService {
    private final UserRepository userRepository;
    public UserService(UserRepository userRepository) {
        this.userRepository = userRepository;
    }
}

5. Inefficient Database Queries

• Mistake: Developers unintentionally cause N+1 query problems by loading collections lazily without batching.
• Solution: Use @EntityGraph or proper fetching strategies to avoid the N+1 query issue.
• Example:

@EntityGraph(attributePaths = {"profile"})
List<User> findAllWithProfile();

6. Neglecting Security Best Practices

• Mistake: Not enabling security features like CSRF, leading to vulnerabilities.
• Solution: Use Spring Security and enable features like CSRF protection.
• Example: Enabling CSRF protection in WebSecurityConfigurerAdapter

@Configuration
public class SecurityConfig extends WebSecurityConfigurerAdapter {
    @Override
    protected void configure(HttpSecurity http) throws Exception {
        http
            .csrf().enable()
            .authorizeRequests().anyRequest().authenticated();
    }
}

7. Mismanaging Bean Scopes

• Mistake: Using the default singleton scope for beans that need to have different lifetimes, such as request-scoped or session-scoped beans.
• Solution: Define appropriate scopes for beans based on your application needs.
• Example:

@Scope("request")
@Component
public class RequestScopedBean {
    // Bean logic
}

8. Ignoring Profiles

• Mistake: Not setting up proper profiles for different environments (development, staging, production).
• Solution: Use Spring Profiles to externalize configuration for different environments.
• Example: Define profiles in application-dev.properties, application-prod.properties, etc.

# application-dev.properties
spring.datasource.url=jdbc:h2:mem:testdb

9. Incorrect Use of @Transactional

• Mistake: Applying @Transactional at the controller level or misunderstanding its behavior.
• Solution: Apply @Transactional at the service layer where your business logic resides, and be mindful of propagation and isolation levels.
• Example:

@Service
public class UserService {
    @Transactional
    public void createUser(User user) {
        userRepository.save(user);
    }
}

10. Neglecting Unit Tests

• Mistake: Focusing solely on integration tests and ignoring unit tests, leading to harder debugging.
• Solution: Use JUnit and Mockito for unit testing and MockMvc for controller tests.
• Example:

@RunWith(SpringRunner.class)
@WebMvcTest(UserController.class)
public class UserControllerTest {
    @Autowired
    private MockMvc mockMvc;

    @Test
    public void shouldReturnUser() throws Exception {
        mockMvc.perform(get("/user/1"))
            .andExpect(status().isOk())
            .andExpect(jsonPath("$.name").value("John"));
    }
}

Conclusion

By being mindful of these common mistakes and applying the best practices in Spring Boot development, you can improve both the performance and maintainability of your applications. Whether you’re dealing with dependency injection, database queries, or security configurations, small changes can significantly enhance your application’s efficiency and resilience.