Spring Boot Best Practices
Your goal is to help me write high-quality Spring Boot applications by following established best practices.
Project Setup & Structure
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Build Tool: Use Maven (
pom.xml) or Gradle (build.gradle) for dependency management.
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Starters: Use Spring Boot starters (e.g.,
spring-boot-starter-web, spring-boot-starter-data-jpa) to simplify dependency management.
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Package Structure: Organize code by feature/domain (e.g.,
com.example.app.order, com.example.app.user) rather than by layer (e.g., com.example.app.controller, com.example.app.service).
Dependency Injection & Components
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Constructor Injection: Always use constructor-based injection for required dependencies. This makes components easier to test and dependencies explicit.
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Immutability: Declare dependency fields as
private final.
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Component Stereotypes: Use
@Component, @Service, @Repository, and @Controller/@RestController annotations appropriately to define beans.
Configuration
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Externalized Configuration: Use
application.yml (or application.properties) for configuration. YAML is often preferred for its readability and hierarchical structure.
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Type-Safe Properties: Use
@ConfigurationProperties to bind configuration to strongly-typed Java objects.
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Profiles: Use Spring Profiles (
application-dev.yml, application-prod.yml) to manage environment-specific configurations.
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Secrets Management: Do not hardcode secrets. Use environment variables, or a dedicated secret management tool like HashiCorp Vault or AWS Secrets Manager.
Web Layer (Controllers)
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RESTful APIs: Design clear and consistent RESTful endpoints.
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DTOs (Data Transfer Objects): Use DTOs to expose and consume data in the API layer. Do not expose JPA entities directly to the client.
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Validation: Use Java Bean Validation (JSR 380) with annotations (
@Valid, @NotNull, @Size) on DTOs to validate request payloads.
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Error Handling: Implement a global exception handler using
@ControllerAdvice and @ExceptionHandler to provide consistent error responses.
Service Layer
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Business Logic: Encapsulate all business logic within
@Service classes.
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Statelessness: Services should be stateless.
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Transaction Management: Use
@Transactional on service methods to manage database transactions declaratively. Apply it at the most granular level necessary.
Data Layer (Repositories)
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Spring Data JPA: Use Spring Data JPA repositories by extending
JpaRepository or CrudRepository for standard database operations.
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Custom Queries: For complex queries, use
@Query or the JPA Criteria API.
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Projections: Use DTO projections to fetch only the necessary data from the database.
Logging
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SLF4J: Use the SLF4J API for logging.
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Logger Declaration:
private static final Logger logger = LoggerFactory.getLogger(MyClass.class);
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Parameterized Logging: Use parameterized messages (
logger.info("Processing user {}...", userId);) instead of string concatenation to improve performance.
Testing
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Unit Tests: Write unit tests for services and components using JUnit 5 and a mocking framework like Mockito.
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Integration Tests: Use
@SpringBootTest for integration tests that load the Spring application context.
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Test Slices: Use test slice annotations like
@WebMvcTest (for controllers) or @DataJpaTest (for repositories) to test specific parts of the application in isolation.
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Testcontainers: Consider using Testcontainers for reliable integration tests with real databases, message brokers, etc.
Security
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Spring Security: Use Spring Security for authentication and authorization.
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Password Encoding: Always encode passwords using a strong hashing algorithm like BCrypt.
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Input Sanitization: Prevent SQL injection by using Spring Data JPA or parameterized queries. Prevent Cross-Site Scripting (XSS) by properly encoding output.
