Dung (Donny) Nguyen

Senior Software Engineer

Spring Boot Annotations Cheat Sheet

In Spring Boot, annotations are a huge part of how you configure and wire your application without tons of XML. Here are some of the most commonly used ones, grouped by purpose so they’re easier to remember:

🚀 Core / Bootstrapping

@SpringBootApplication The main annotation for a Spring Boot app. It combines:
- @Configuration
- @EnableAutoConfiguration
- @ComponentScan You usually put this on your main class.
@Configuration Marks a class as a source of bean definitions.
@Bean Declares a method that returns an object managed by Spring (a “bean”).

🔍 Component Scanning & Dependency Injection

@Component Generic stereotype for any Spring-managed component.
@Service Specialized version of @Component for service-layer classes.
@Repository Used for DAO (data access) classes; also enables exception translation.
@Controller Marks a class as a web controller (MVC).
@RestController Combines @Controller + @ResponseBody for REST APIs.
@Autowired Injects dependencies automatically.
@Qualifier Used with @Autowired when multiple beans exist.

🌐 Web / REST Annotations

@RequestMapping Maps HTTP requests to handler methods.
@GetMapping, @PostMapping, @PutMapping, @DeleteMapping Shortcut annotations for specific HTTP methods.
@PathVariable Extracts values from the URL path.
@RequestParam Gets query parameters.
@RequestBody Binds HTTP request body to a Java object.
@ResponseBody Sends return value directly as HTTP response (usually JSON).

🗄️ Data / JPA Annotations

(Used with Spring Data JPA and ORM tools)

@Entity Marks a class as a database entity.
@Id Specifies the primary key.
@GeneratedValue Defines how the primary key is generated.
@Table Specifies the table name.
@Column Maps a field to a column.

⚙️ Configuration & Properties

@Value Injects values from properties files.
@ConfigurationProperties Binds external config (like application.yml) to a Java class.

🔐 Validation

@Valid Triggers validation on request bodies.
Common Java validation annotations:
- @NotNull
- @Size
- @Email

🔄 Transactions

@Transactional Manages database transactions automatically.

🧪 Testing

@SpringBootTest Loads the full application context for tests.
@MockBean Adds mocks into the Spring context.