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.