Commonly Used Spring Framework Annotations and Their Usage

Spring introduced annotation support starting from Java 5, and since Spring 2.5 the framework has gradually moved away from XML configuration toward annotation‑based configuration.

Core Annotations

@Required

is placed on a bean's setter to indicate that the property must be injected, otherwise a BeanInitializationException is thrown. @Autowired can be used on fields, setters, or constructors to declare a dependency that Spring should inject by type. Example of field injection:

@Component
public class User {
    @Autowired
    private Address address;
}

Setter injection allows custom logic:

@Component
public class User {
    private Address address;

    @Autowired
    public void setAddress(Address address) {
        // custom code
        this.address = address;
    }
}

Constructor injection (only one constructor may be annotated; from Spring 4.3 it is optional when there is a single constructor):

@Component
public class User {
    private Address address;

    @Autowired
    public User(Address address) {
        this.address = address;
    }
}

@Qualifier

works together with @Autowired to disambiguate beans of the same type:

@Component
public class User {
    @Autowired
    @Qualifier("address1")
    private Address address;
}

@Configuration

marks a class as a source of bean definitions, similar to an XML configuration file. Methods annotated with @Bean define individual beans:

@Configuration
public class SpringCoreConfig {
    @Bean
    public AdminUser adminUser() {
        AdminUser adminUser = new AdminUser();
        return adminUser;
    }
}

@ComponentScan

is usually paired with @Configuration to specify the packages that Spring should scan for annotated components. @Lazy can be placed on a component or on a @Configuration class to defer bean initialization until the bean is first needed. @Value injects property values using Spring Expression Language (SpEL) or placeholder syntax (${…}) into fields, constructor parameters, or method parameters.

Spring MVC and REST Annotations

@Controller

marks a class as a Spring MVC controller (a specialized @Component). @RequestMapping maps HTTP requests to handler classes or methods. It can define a base URL at the class level and specific URLs or HTTP methods at the method level. Example:

@Controller
@RequestMapping("/users")
public class UserController {
    @RequestMapping(method = RequestMethod.GET)
    public String getUserList() {
        return "users";
    }
}

Since Spring 4.3, shortcut annotations such as @GetMapping, @PostMapping, @PutMapping, @PatchMapping, and @DeleteMapping replace @RequestMapping for the corresponding HTTP methods. @CookieValue binds a specific cookie value to a method parameter:

@RequestMapping("/cookieValue")
public void getCookieValue(@CookieValue("JSESSIONID") String cookie) { }

@CrossOrigin

enables CORS support on a controller or method:

@CrossOrigin(maxAge = 3600)
@RestController
@RequestMapping("/users")
public class AccountController {
    @CrossOrigin(origins = "http://xx.com")
    @RequestMapping("/login")
    public Result userLogin() {
        // ...
    }
}

Exception handling, data binding, and model attributes are managed with @ExceptionHandler, @InitBinder, @ModelAttribute, @RequestAttribute, @RequestBody, @RequestHeader, @RequestParam, @RequestPart, @ResponseBody, @ResponseStatus, @ControllerAdvice, @RestController, @RestControllerAdvice, @SessionAttribute, and @SessionAttributes.

Matrix variables can be used with @MatrixVariable but require enabling support:

<mvc:annotation-driven enable-matrix-variables="true"/>

Programmatic enabling via Java configuration:

@Configuration
public class WebConfig extends WebMvcConfigurerAdapter {
    @Override
    public void configurePathMatch(PathMatchConfigurer configurer) {
        UrlPathHelper urlPathHelper = new UrlPathHelper();
        urlPathHelper.setRemoveSemicolonContent(false);
        configurer.setUrlPathHelper(urlPathHelper);
    }
}

Spring Boot Annotations

@EnableAutoConfiguration

tells Spring Boot to automatically configure beans based on the classpath. @SpringBootApplication is a convenience annotation that combines @Configuration, @EnableAutoConfiguration, and @ComponentScan for the main application class.

Stereotype Annotations

@Component

declares a generic Spring bean. @Service and @Repository are specializations of @Component for service and data‑access layers, respectively. The latter also enables exception translation.

Data Access Annotation

@Transactional

marks a class or method as participating in a transaction. It is metadata consumed by transaction‑management infrastructure.

Task Execution and Scheduling Annotations

@Scheduled

schedules a method for periodic execution. Example with fixed delay and fixed rate:

@Scheduled(fixedDelay = 1000)
public void schedule() { }

@Scheduled(fixedRate = 1000)
public void schedulg() { }

@Async

runs a method asynchronously in a separate thread. The method may return a Future or be void.

Testing Annotations

Integration tests can be configured with @RunWith(SpringJUnit4ClassRunner.class) and @ContextConfiguration to load the Spring context:

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(classes = SpringCoreConfig.class)
public class UserServiceTest { }

These annotations together provide a comprehensive, annotation‑driven approach to building, configuring, testing, and operating modern Spring‑based Java applications.