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

java-springboot