[Spring] Spring Annotations and Concepts

Spring Annotations

/ Annotations /

Annotation	Description
@Configuration	Indicates that a class declares one or more @Bean methods and may be processed by the Spring container to generate bean definitions
@ComponentScan	Define specific packages to scan for components. if specific packages are not defined, scanning will occur from the package of the class that declares this annotation
@Bean	Indicates that a method produces a bean to be managed by the Spring container
@Component	Indicates that an annotated class is a “component”
@Service	Specialization of @Component indicating that an annotated class has business logic
@Controller	Specialization of @Component indicating that an annotated class is a “Controller” (e.g. a web controller). Used to define controllers in your web applications and REST API
@Repository	Specialization of @Component indicating that an annotated class is used to retrieve and/or manipulate data in a database
@Primary	Indicates that a bean should be given preference when multiple candidates are qualified to autowire a single-valued dependecy
@Qualifier	Used on a field or parameter as a qualifier for candidate beans when autowiring
@Lazy	Indicates that a bean has to be lazily initialized. Absence of @Lazy annotation will lead to eager initialization.
@Scope (Value= ConfigurableBeanFactory.SCOPE_PROTOTYPE)	Defines a bean to be prototype - a new instance will be created every time you refer to the bean. Default scope is a singleton - one instance per IOC container.
@PostConstruct	Identifies the method that will be executed after dependency injection is done to perform any initialization
@PreDestory	Identifies the method that will receive the callback notification to signal that the instance is in the process of being removed by the container. Typically used to release resources that it has been holding.
@Named	Jakarta Contexts & Dependency Injection (CDI) Annotation similar to @Component
@Inject	Jakarta Contexts & Dependency Injection (CDI) Annotation similar to @Autowired

Spring Concepts

Concept	Description
Dependency Injection	Identify beans, their dependencies and wire them together (provices IOC - Inversion of Control)
Constr.injection	Dependencies are set by creating the Bean using its Constructor
Setter injection	Dependencies are set by calling setter methods on your beans
Field injection	No setter or constructor. Dependency is injected using reflection
IOC Container	Spring IOC Context that manages Spring Beans & their lifecycle
Bean Factory	Basic Spring IOC Container
Application Context	Advanced Spring IOC Container with enterprise-specific features - Easy to use in web applications with internationalization features and good integration with Spring AOP
Spring Beans	Objects managed by Spring
Auto-wiring	Process of wiring in dependencies for a Spring Bean