Comprehensive Guide to Spring MVC, Bean, and Boot Annotations

1. Spring Web MVC Annotations

The @RequestMapping annotation maps HTTP requests to handler methods and is supported by RequestMappingHandlerMapping and RequestMappingHandlerAdapter. It offers six attributes: value, method, params, header, consume, and product. Before using it, the class must be annotated with @Controller or @RestController.

Examples include class‑level @RequestMapping to prefix all method paths and method‑level usage for specific URLs.

@RequestBody

@RequestBody

binds the request body to a method parameter via HttpMessageConverter and can be combined with @Valid for validation.

@GetMapping, @PostMapping, @PutMapping, @DeleteMapping, @PatchMapping

These are shortcut annotations for @RequestMapping with specific HTTP methods (GET, POST, PUT, DELETE, PATCH). Each example shows the typical usage pattern.

@ControllerAdvice

Marks a class as a global exception handler and allows the use of @ExceptionHandler, @InitBinder, and @ModelAttribute to process exceptions, data binding, and model attributes across all controllers.

2. Spring Bean Annotations

@ComponentScan

configures the packages to scan for components. @Component marks a generic bean, while @Service, @Repository, and @Controller are specialized stereotypes for business logic, DAO, and MVC controllers respectively.

3. Dependency Injection and Scope Annotations

@Autowired

injects dependencies on constructors, fields, or setter methods. @Primary gives a bean higher priority when multiple candidates exist. @Qualifier disambiguates injection by name. @Bean defines a bean method; its initMethod and destroyMethod attributes control lifecycle callbacks. @DependsOn forces bean initialization order. @Scope specifies bean scope such as singleton, prototype, request, session, etc. Example shows prototype usage with ConfigurableBeanFactory.SCOPE_PROTOTYPE.

4. Spring Boot Configuration Annotations

@SpringBootApplication

combines @Configuration, @EnableAutoConfiguration, and @ComponentScan. @EnableAutoConfiguration triggers auto‑configuration based on classpath dependencies.

Conditional annotations ( @ConditionalOnClass, @ConditionalOnMissingClass, @ConditionalOnBean, @ConditionalOnMissingBean, @ConditionalOnProperty, @ConditionalOnResource, @ConditionalOnWebApplication, @ConditionalOnNotWebApplication) enable or disable beans/configurations based on the presence of classes, beans, properties, resources, or application type.

Lifecycle annotations from JSR‑250, @PostConstruct and @PreDestroy, are used for initialization and cleanup methods.

5. Summary

The article consolidates the most commonly used Spring MVC, Spring Bean, dependency‑injection, scope, and Spring Boot conditional annotations, providing clear explanations and code snippets to help Java backend developers apply these annotations effectively in real projects.