Spring Boot Annotations and Concepts

Flashcards covering key Spring Boot annotations, concepts, and usage scenarios.

@SpringBootApplication

Marks the main class of a Spring Boot application, combines @Configuration, @EnableAutoConfiguration, and @ComponentScan.

@Autowired

Automatically injects dependencies by type for fields, constructors, setters, or methods.

@Component

Marks a class as a Spring-managed component (bean), used for generic components to be autodetected by classpath scanning.

@ComponentScan

Tells Spring where to scan for components, allowing customization beyond the default package.

@Bean

Declares a bean explicitly, usually in a @Configuration class, for when a bean isn't autodetected.

@Service

Specialized @Component for the business logic layer, for classes that perform service-level logic.

@Repository

Specialized @Component for persistence logic that interacts with the database and provides exception translation.

@Configuration

Marks a class for bean definitions via @Bean methods, used for Java-based bean configuration.

@EnableAutoConfiguration

Auto-configures Spring beans based on the classpath to reduce boilerplate.

@Qualifier

Resolves ambiguity when multiple beans of the same type exist by specifying which bean to inject.

@Primary

Designates a default bean to be injected when multiple candidates exist.

@DependsOn

Ensures one bean is initialized before another when bean initialization order matters.

@Profile

Loads a bean/configuration for a specific environment, such as development or production.

@Import

Imports other configuration classes to modularize configuration into separate files.

@ImportResource

Imports XML configuration files, integrating legacy Spring XML config.

@PropertySource

Loads properties from a file into Spring Environment, used to externalize configuration values.

Retention Policy in Java Annotations

Defines annotation lifespan; SOURCE discarded during compile, CLASS retained in .class file, RUNTIME retained for reflection during runtime.

ElementType in Java Annotations

Defines valid annotation targets, such as TYPE, METHOD, FIELD, PARAMETER, CONSTRUCTOR.

@RestController

Combines @Controller and @ResponseBody, used to create RESTful web services.

@RequestMapping

Maps HTTP requests to handler methods for flexible route mappings.

@GetMapping

Shorthand for @RequestMapping( method = RequestMethod.GET ), for read-only REST endpoints.

@PostMapping

Handles HTTP POST requests for creating or submitting resources.

@PutMapping

Handles HTTP PUT requests for updating existing resources.

@DeleteMapping

Handles HTTP DELETE requests for deleting resources.

@RequestParam

Binds request parameters to method arguments, allowing access to query parameters.

@PathVariable

Extracts values from URI path, useful for REST endpoints with dynamic values.

@RequestBody

Maps request JSON to Java object, handling input for POST or PUT requests.

@ResponseBody

Indicates the return value is serialized to the response body.

SpringApplication.run()

Bootstraps and launches a Spring application, serves as the entry point for running Spring Boot apps.

application.properties

Configuration file for Spring Boot apps, used to set properties like server port and database config.

application.yml

Alternative to application.properties using YAML syntax for hierarchical and cleaner configuration.

@Value

Injects property values from configuration files into fields.

@ConfigurationProperties

Binds properties to a POJO for organized and type-safe configuration mapping.

CommandLineRunner

Executes code after the app starts, used for initial setup logic like seeding data.

Actuator

Provides production-ready features like metrics and health checks for Spring Boot apps.

Spring DevTools

Offers live reload, auto-restart, and developer-friendly settings to accelerate development feedback loop.

Spring Boot Starter

A curated set of dependencies for specific functionality, simplifying dependency management.

Embedded Server in Spring Boot

Spring Boot apps run with an embedded server like Tomcat or Jetty, eliminating the need for external deployment.

@Transactional

Declares that a method should be executed within a transaction to maintain data consistency.

@ControllerAdvice

Handles exceptions globally across the whole application for centralized error handling.

Spring Security

Framework for authentication and authorization in Spring apps, securing REST APIs, login, roles, and permissions.

Spring Boot Test

Testing support for Spring Boot applications, particularly integration tests with embedded containers.

MockMvc

Utility for testing Spring MVC controllers without starting a server, used for unit testing controller logic.

TestRestTemplate

Helper class for integration testing RESTful services, testing the full HTTP lifecycle.

Spring Boot Auto Configuration

Automatically configures beans based on classpath, properties, and environment to simplify configuration.

@ConditionalOnProperty

Conditionally loads beans based on the presence or value of a property to enable or disable features.

@Conditional

Enables bean registration based on custom conditions, allowing programmatic bean registration.

Spring Boot Profiles

Environment-specific configuration mechanism used to set different configs for dev, test, and prod.

@RestTemplate

Client for performing REST calls, useful for calling external services.

WebClient

Reactive, non-blocking alternative to RestTemplate, used for async API calls in reactive applications.

Health Indicators

Custom or built-in checks for service health, exposing the /actuator/health endpoint.

Spring Boot Metrics

Tracks application metrics like memory, GC, custom counters for performance monitoring.

Spring Boot Logging

Uses SLF4J with Logback by default, allowing customization of logging levels and outputs.

Spring Boot Caching

Enables method-level caching to improve performance by caching expensive operations.

Spring Data JPA

Abstraction over JPA for simplified database access, allowing declaration of interfaces for CRUD operations.

Spring Boot JPA Auditing

Tracks entity creation and modification timestamps, automatically populating fields like createdAt and updatedAt.

Flyway / Liquibase

Version control for database schema, allowing tracking, applying, and rolling back DB migrations safely.