Core Annotations Cheat Sheet
A reference table of the core annotations you'll see across a typical Spring Boot codebase.
| Annotation | Purpose |
|---|
@SpringBootApplication | Entry point; combines @Configuration, @EnableAutoConfiguration, @ComponentScan |
@Configuration | Marks a class as a source of bean definitions |
@Bean | Declares a bean inside a @Configuration class |
@ConfigurationProperties | Binds a config block to a POJO |
@Profile("dev") | Only load a bean/config under a given active profile |
@Conditional* | Register a bean only if a condition holds (used heavily in auto-config) |
| Annotation | Purpose |
|---|
@Component | Generic Spring-managed bean |
@Service | Business/service layer bean (semantic alias of @Component) |
@Repository | Data access layer bean; adds exception translation |
@Controller | Web layer bean returning views |
@RestController | @Controller + @ResponseBody; returns data (JSON) directly |
| Annotation | Purpose |
|---|
@Autowired | Injects a dependency (optional on constructors since Spring 4.3 if there's only one constructor) |
@Qualifier("beanName") | Disambiguates when multiple beans of the same type exist |
@Primary | Marks a bean as the default choice when multiple candidates exist |
@Lazy | Delays bean initialization until first use |
| Annotation | Purpose |
|---|
@RequestMapping | Base mapping for a controller/method (path, method, etc.) |
@GetMapping / @PostMapping / @PutMapping / @DeleteMapping / @PatchMapping | Shortcut HTTP-method mappings |
@PathVariable | Binds a URI template variable to a method param |
@RequestParam | Binds a query parameter |
@RequestBody | Deserializes the request body into a Java object |
@ResponseBody | Serializes the return value into the response body |
@ResponseStatus | Sets the HTTP status for a response/exception |
@CrossOrigin | Enables CORS for a controller/method |
| Annotation | Purpose |
|---|
@Valid / @Validated | Triggers bean validation on a @RequestBody or method params |
@NotNull, @NotBlank, @Size, @Email, @Min/@Max | Field-level constraints (from jakarta.validation) |
| Annotation | Purpose |
|---|
@Entity | Marks a class as a JPA-managed table |
@Id / @GeneratedValue | Primary key + generation strategy |
@Column | Column-level customization |
@OneToMany, @ManyToOne, @ManyToMany | Relationship mappings |
@Transactional | Wraps a method in a database transaction |
Don't sprinkle @Autowired field injection everywhere just because it
"compiles." Constructor injection (covered in the IoC/DI topic) is the
convention in real codebases and what you should default to.
Last updated on July 15, 2026
