Essential MyBatis, Spring MVC, Spring, SpringBoot & Lombok Annotations Explained

Preface

OOP (Object‑Oriented Programming), IoC (Inversion of Control), AOP (Aspect‑Oriented Programming) are programming paradigms, and DI (Dependency Injection) is a concrete implementation of IoC.

1. Common MyBatis Annotations

@Select – query operation.

@Insert – insert operation.

@Update – update operation.

@Delete – delete operation.

@Mapper – generates a proxy object for the Mapper interface and registers it in the IoC container.

@MapperScan – eliminates the need to annotate each Mapper with @Mapper; specify the package to automatically generate proxies for all Mapper interfaces in that package.

2. Common Spring MVC Annotations

@RequestMapping – placed on methods to define endpoint paths (often used for id‑based queries/deletes) or on classes to define a module prefix (e.g., "/users").

@RequestParam – maps a request parameter (key=value) to a method argument when names differ.

@RequestBody – binds a JSON string from a POST request to a method argument.

@ResponseBody – returns a raw string or converts an object to JSON (requires Jackson).

@PathVariable – extracts a path variable (e.g., "/users/1") and binds it to a method parameter.

@GetMapping – GET request for query operations.

@PostMapping – POST request for add/create operations.

@PutMapping – PUT request for update operations.

@DeleteMapping – DELETE request for delete operations. These four follow REST conventions, widely adopted in enterprise development.

3. Common Spring Annotations

1. IoC Annotations

@Controller – creates a controller bean in the IoC container.

@Service – creates a service bean in the IoC container.

@Repository – creates a mapper/repository bean in the IoC container.

@Component – creates a generic bean (neither controller, service, nor mapper) in the IoC container.

@Configuration + @Bean – @Configuration marks a class as a configuration source; @Bean on a method registers the method’s return object as a bean.

@RestController – combines @Controller and @ResponseBody, so individual methods need not be annotated with @ResponseBody.

2. DI Annotations

@Value – injects basic types such as String.

@Autowired – injects custom or third‑party objects.

3. Transaction Annotations

@Transactional – typically placed on service‑layer methods to manage transactions: it starts a transaction before method execution, commits on success, and rolls back on failure.

Note: By default, runtime exceptions trigger a rollback, while checked exceptions do not; you can use the rollbackFor attribute to specify additional exception types. If a try‑catch block handles the exception, the transaction will not roll back.

4. Common SpringBoot Annotations

@SpringBootApplication – marks the main class of a SpringBoot application (entry point).

@SpringBootTest – indicates a test class for SpringBoot unit testing.

5. Lombok Annotations

@NoArgsConstructor – generates a no‑argument constructor.

@AllArgsConstructor – generates an all‑argument constructor.

@Getter – generates getter methods.

@Setter – generates setter methods.

@ToString – generates a toString method.

@EqualsAndHashCode – generates equals and hashCode methods.

@Data – combines @Getter, @Setter, @ToString, @EqualsAndHashCode, and also generates required constructors.

Summary: Using @NoArgsConstructor, @AllArgsConstructor, and @Data together usually suffices.