• 빈 연결 (bean wiring) : ex) dataSouce, transaction manager, kafka listener ...
• 속성 주입 (property injection) ex) db host, id, pw , ssl keystore , user custom properties (no hardcoding)

• spring boot 에서는 대부분 자동화 (starter), 수동 설정하여 override 가능

참고 ) https://velog.io/@ashappyasikonw/SPRING-BOOT-%EC%99%B8%EB%B6%80-%EC%84%A4%EC%A0%95-%EB%B0%8F-%EC%9A%B0%EC%84%A0%EC%88%9C%EC%9C%84-Externalized-Configuration-and-priorities

• cli argument
• ServletContext init parameter
• JNDI attribute
• java system properties (System.getProperties())
• OS env param (EXPORT SPRING_ACTIVE_PROFILES=prod)

랜덤한 미사용 포트로 동작한다

micro 서비스 환경 혹은 test 시에 유용하다

logging:
  path: /val/logs/
  file: TacoCloud.log
  level:
    root: warn
    org:
      springframework:
        security: debug

...
greeting:
  welcome: ${spring.application.name}

taco:
  props:
    size: 10
    prize: 1000
    name: 존맛탱타코

@Component
@ConfigurationProperties(prefix="taco.props")
@Getter
public class TacoProps {
	private int size;

	@Min(value=5, message="must be between 5 and 5000")
	@Max(value=5000, message="must be between 5 and 5000")
	private long prize;
	private String name;
}

...

@Service
public class TacoServiceImpl {

    @AutoWired
    private TacoProps tacoProps;

	....

}

• 없어도 동작에 이상 없지만, 구성속성 정보를 제공해주므로 개발시 편리하다
• spring-boot-configuration-processor 의존성 추가

ex)src/main/resources/META-INF/additional-spring-configuration-metadata.json
{
	properties: [
		{
			name: "taco.orders.page-size",
			type: "int",
			description: "user custom properties meta into sample"
		}
	]
}

logging:
  level:
    root: warn

---
spring:
  profiles: prod
  datesource:
    url: jdbc:mysql://10.10.20.30/prod-db

---
spring:
  profiles: dev
  datasource:
    url: jdbc:mysql://10.100.200.100/dev-db

java -jar app.jar --spring.profiles,active=prod

or

export SPRING_PROFILES_ACTIVE=prod

@Bean
@Profile("dev")
public DevDataSourceConfiguration { 
...
}

@Bean
@Profile("prod")
public ProdDataSourceConfiguration { 
...
}

@Bean
@Profile("!prod")
public NotProdDataSourceConfiguration { 
...
}