Spring boot Annotations

• Java annotations are just metadata and read by annotation processors
• They are not decorators

Common Examples:

@Bean @Service → stereotype around @Component @Component @ComponentScan @SpringBootTest @SpringBoot @Configuration @ConfigurationProperties @EnableConfigurationProperties @SpringBootApplication @Repository @Controller @RestController @Transactional

@SpringBootApplication

• https://docs.spring.io/spring-boot/reference/using/using-the-springbootapplication-annotation.html
• Starting point of spring boot app
  • acts as a configuration file
  • starting point of component scan
  • initiates auto configuration that is part of spring boot itself

• This annotation combines following annotations with their default attributes:
  • @EnableAutoConfiguration
    • enable Spring Boot’s auto-configuration mechanism
  • @ComponentScan
    • scan on the package for @Component
  • @SpringBootConfiguration
    • enable registration of extra beans in the context or the import of additional configuration classes.
    • Similar to @Configuration

Stereotype Annotations

• Stereotype annotations specialized annotations that are used to indicate the role or purpose of a particular component
• examples:
  • @Component (main stereotype annotation)
    • @Service (indicate Service)
    • @Repository (indicate repository)
    • @Controller (indicate Controller)
    • @Configuration

@Import

• used to import additional configuration classes.
• Alternatively, you can use @ComponentScan to automatically pick up all Spring components, including @Configuration classes.

More annotations

• @Import
• @ComponentScan
• @PropertySource
• @Order

@Configuration
@EnableAutoConfiguration
@Import({
        BeaconWebConfig.class,
        BeaconServiceWebConfigCustomizer.class,
        BeaconHealthIndicatorConfig.class
})
@ComponentScan({
        "com.xyz.beacon.controllers",
        "com.xyz.beacon.legacy.controllers",
})
@PropertySource(value = "classpath:beacon-web-config.yaml", factory = BeaconInternalYamlPropertySourceFactory.class)
@Order(1)
public class BeaconServiceWebConfig implements WebMvcConfigurer, ApplicationContextAware {}

Custom Annotations and practical example

• Annotation Processor
• ????