Springboot

# Spring Boot Development

General Instructions

- Make only high confidence suggestions when reviewing code changes.

- Write code with good maintainability practices, including comments on why certain design decisions were made.

- Handle edge cases and write clear exception handling.

- For libraries or external dependencies, mention their usage and purpose in comments.

Spring Boot Instructions

Dependency Injection

- Use constructor injection for all required dependencies.

- Declare dependency fields as `private final`.

Configuration

- Use YAML files (`application.yml`) for externalized configuration.

- Environment Profiles: Use Spring profiles for different environments (dev, test, prod)

- Configuration Properties: Use @ConfigurationProperties for type-safe configuration binding

- Secrets Management: Externalize secrets using environment variables or secret management systems

Code Organization

- Package Structure: Organize by feature/domain rather than by layer

- Separation of Concerns: Keep controllers thin, services focused, and repositories simple

- Utility Classes: Make utility classes final with private constructors

Service Layer

- Place business logic in `@Service`-annotated classes.

- Services should be stateless and testable.

- Inject repositories via the constructor.

- Service method signatures should use domain IDs or DTOs, not expose repository entities directly unless necessary.

Logging

- Use SLF4J for all logging (`private static final Logger logger = LoggerFactory.getLogger(MyClass.class);`).

- Do not use concrete implementations (Logback, Log4j2) or `System.out.println()` directly.

- Use parameterized logging: `logger.info("User {} logged in", userId);`.

Security & Input Handling

- Use parameterized queries | Always use Spring Data JPA or `NamedParameterJdbcTemplate` to prevent SQL injection.

- Validate request bodies and parameters using JSR-380 (`@NotNull`, `@Size`, etc.) annotations and `BindingResult`

Build and Verification

- After adding or modifying code, verify the project continues to build successfully.

- If the project uses Maven, run `mvn clean package`.

- If the project uses Gradle, run `./gradlew build` (or `gradlew.bat build` on Windows).

- Ensure all tests pass as part of the build.

Useful Commands

| Gradle Command | Maven Command | Description |

|:--------------------------|:----------------------------------|:----------------------------------------------|

| `./gradlew bootRun` |`./mvnw spring-boot:run` | Run the application. |

| `./gradlew build` |`./mvnw package` | Build the application. |

| `./gradlew test` |`./mvnw test` | Run tests. |

| `./gradlew bootJar` |`./mvnw spring-boot:repackage` | Package the application as a JAR. |

| `./gradlew bootBuildImage`|`./mvnw spring-boot:build-image` | Package the application as a container image. |