외부 설정 사용 - Environment

외부 설정

• 설정 파일
  • application.properties
  • ...
• Environment Variables
• JVM System Properties
• Command Line Arguments

Spring이 지원하는 다양한 외부 설정 조회 바법

• Environment
• @Value
• @ConfigurationProperties

Environment - 외부 설정 사용

• Environment::getProperty(String) : String
• Environment::getProperty(String, Class<T>) : T

@Configuration
@RequiredArgsConstructor
@Slf4j
public class MyDataSourceEnvironmentConfig {

    private final Environment environment;

    @Bean
    public MyDataSource myDataSource() {
        String url = environment.getProperty("my.datasource.url");
        String username = environment.getProperty("my.datasource.username");
        String password = environment.getProperty("my.datasource.password");
        
        int maxConnection = environment.getProperty("my.datasource.etc.max-connection", Integer.class);
        var timeout = environment.getProperty("my.datasource.etc.timeout", Duration.class);
        var options = environment.getProperty("my.datasource.etc.options", List.class);

        return new MyDataSource(url, username, password, maxConnection, timeout, options);
    }
}

my.datasource.url=local.db.com
my.datasource.username=local_user
my.datasource.password=local_password
my.datasource.etc.max-connection=1
my.datasource.etc.timeout=3500ms
my.datasource.etc.options=CACHE,ADMIN

명명 규칙

• kebab-case
• camelCase
• snake_case
• PascalCase

참고: Spring에서 제공하는 속성 변환기

Configuration Properties Type Conversion

• java.time.Duration
  • Conversion Duration
• java.time.Period
  • Conversion Period
• org.springframework.util.unit.DataSize
  • Conversion DataSize

@Value - 외부 설정 사용

• @Value에 ${...} 을 사용해서 외부 설정의 키 값을 주면 원하는 값을 주입 받을 수 있다.
  • ${property-placeholder-style}
  • #{SpEL}
• @Value 는 필드, 파라미터 등 사용할 수 있다.
• Default Value 설정도 가능하다.
  • @Value("${key:default-value}")

@Target({ElementType.FIELD, ElementType.METHOD, ElementType.PARAMETER, ElementType.ANNOTATION_TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Value {
    String value();
}

@Value 사용 예시

@Configuration
@Slf4j
public class MyDataSourceValueConfig {
    @Value("${my.datasource.username}")
    private String url;

    @Value("${my.datasource.username}")
    private String username;

    @Value("${my.datasource.password}")
    private String password;

    @Value("${my.datasource.etc.max-connection:1}")
    private int maxConnection;

    @Value("${my.datasource.etc.timeout:PT10S}")
    private Duration timeout;

    @Value("${my.datasource.etc.options}")
    private List<String> options;

    @Bean
    public MyDataSource myDataSource1() {
        return new MyDataSource(url, username, password, maxConnection, timeout, options);
    }

    @Bean
    public MyDataSource myDataSource2(
        @Value("${my.datasource.username}") String url,
        @Value("${my.datasource.username}") String username,
        @Value("${my.datasource.password}") String password,
        @Value("${my.datasource.etc.max-connection:1}") int maxConnection,
        @Value("${my.datasource.etc.timeout:PT10S}") Duration timeout,
        @Value("${my.datasource.etc.options}") List<String> options
    ) {
        return new MyDataSource(url, username, password, maxConnection, timeout, options);
    }
}

@ConfigurationProperties - 외부 설정 사용

• Spring은 외부 설정의 묶음 정보를 객체로 변환하는 기능을 제공한다.
• Type-safe Configuration Properties

@ConfigurationProperties("my.datasource")
public record MyDataSourcePropertiesV2(
    String url,
    String username,
    String password,
    @DefaultValue Etc etc
) {
    public record Etc(
        @DefaultValue("1") int maxConnection,
        @DefaultValue("PT30S") Duration timeout,
        @DefaultValue("DEFAULT") List<String> options
    ) { }
}

@ConfigurationPropertiesScan

• @ConfigurationProperties를 하나 하나 직접 등록할 때는 @EnableConfigurationProperties를 사용한다.
• @ConfigurationProperties를 패키지 범위로 자동 등록할 때는 @ConfigurationPropertiesScan을 사용한다.

@EnableConfigurationProperties 사용 예시 (직접 등록)

@EnableConfigurationProperties(MyDataSourcePropertiesV2.class)
@RequiredArgsConstructor
public class MyDataSourceConfigV2 {
  private final MyDataSourcePropertiesV2 myDataSourceProperties;

  @Bean
  public MyDataSource myDataSource() {
    return new MyDataSource(
            myDataSourceProperties.url(),
            myDataSourceProperties.username(),
            myDataSourceProperties.password(),
            myDataSourceProperties.etc().maxConnection(),
            myDataSourceProperties.etc().timeout(),
            myDataSourceProperties.etc().options()
    );
  }
}

@ConfigurationPropertiesScan 사용 예시 (자동 등록)

@Import(MyDataSourceConfigV2.class)
@ConfigurationPropertiesScan(basePackageClasses = MyDataSourcePropertiesV2.class)
@SpringBootApplication(scanBasePackageClasses = MyDataSource.class)
public class ExternalReadApplication {

    public static void main(String[] args) {
        SpringApplication.run(ExternalReadApplication.class, args);
    }
}

@ConfigurationProperties + @Validated

• @ConfigurationProperties는 @Validated를 지원한다.
  • Java Bean 검증기를 사용할 수 있다.
• org.springframework.boot:spring-boot-starter-validation 의존성 추가 필요
• @Validated 사용

dependencies {
    implementation 'org.springframework.boot:spring-boot-starter-validation'
}

@ConfigurationProperties("my.datasource")
@Validated
public record MyDataSourcePropertiesV3(
    @NotEmpty String url,
    @NotEmpty String username,
    @NotEmpty String password,
    @DefaultValue Etc etc
) {
    public record Etc(
        @Min(1) @Max(999) @DefaultValue("1") int maxConnection,
        @DurationMin(seconds = 1) @DurationMax(seconds = 60)
        @DefaultValue("PT30S") Duration timeout,
        @DefaultValue("DEFAULT") List<String> options
    ) { }
}

application.yaml

YAML (YAML Ain't Markup Language) 은 사람이 읽기 좋은 데이터 구조를 목표로 한다.

• application.properties, application.yaml 둘 다 있을 경우
  • application.properties 우선 순위가 높다.

my.datasource.url=local.db.com
my.datasource.username=local_user
my.datasource.password=local_password
my.datasource.etc.max-connection=1
my.datasource.etc.timeout=35s
my.datasource.etc.options=CACHE,ADMIN

my:
  datasource:
    url: local.db.com
    username: local_user
    password: local_password
    etc:
      max-connection: 1
      timeout: 35s
      options:
      - CACHE
      - ADMIN

application.yaml 에서 profile 분리

• ---, spring.config.activate.on-profile 로 분리

my:
  datasource:
    url: local.db.com
    username: local_user
    password: local_password
    etc:
      max-connection: 1
      timeout: 35s
      options:
      - LOCAL
      - CACHE
---
spring:
  config:
    activate:
      on-profile: dev
my:
  datasource:
    url: dev.db.com
    username: dev_user
    password: dev_password
    etc:
      max-connection: 10
      timeout: 60s
      options:
      - DEV
      - CACHE
---
spring:
  config:
    activate:
      on-profile: prod
my:
  datasource:
    url: prod.db.com
    username: prod_user
    password: prod_password
    etc:
      max-connection: 50
      timeout: 10s
      options:
      - PROD
      - CACHE

@Profile

• @Profile 을 사용해서 profile 별로 등록되는 스프링 Bean을 분리할 수 있다.
• @Conditional, ProfileCondition 을 통해 기능 제공

@Conditional(ProfileCondition.class)
public @interface Profile {

	String[] value();

}

class ProfileCondition implements Condition {

	@Override
	public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
		MultiValueMap<String, Object> attrs = metadata.getAllAnnotationAttributes(Profile.class.getName());
		if (attrs != null) {
			for (Object value : attrs.get("value")) {
				if (context.getEnvironment().acceptsProfiles(Profiles.of((String[]) value))) {
					return true;
				}
			}
			return false;
		}
		return true;
	}

}