Spring Boot YAML vs Properties: 설정 파일 비교 및 면접 질문 2026

# application.properties
server.port=8080
server.servlet.context-path=/api

spring.datasource.url=jdbc:postgresql://localhost:5432/mydb
spring.datasource.username=admin
spring.datasource.password=secret
spring.datasource.driver-class-name=org.postgresql.Driver

spring.jpa.hibernate.ddl-auto=update
spring.jpa.show-sql=true
spring.jpa.properties.hibernate.format_sql=true

# application.yml
server:
  port: 8080
  servlet:
    context-path: /api

spring:
  datasource:
    url: jdbc:postgresql://localhost:5432/mydb
    username: admin
    password: secret
    driver-class-name: org.postgresql.Driver
  jpa:
    hibernate:
      ddl-auto: update
    show-sql: true
    properties:
      hibernate:
        format_sql: true

# application.properties (공통 설정)
spring.application.name=my-application
logging.level.root=INFO

# application-dev.properties
server.port=8080
spring.datasource.url=jdbc:postgresql://localhost:5432/devdb
logging.level.com.example=DEBUG

# application-prod.properties
server.port=80
spring.datasource.url=jdbc:postgresql://prod-db:5432/proddb
logging.level.com.example=WARN

# application.yml
spring:
  profiles:
    active: dev

---
spring:
  config:
    activate:
      on-profile: dev
server:
  port: 8080
logging:
  level:
    root: DEBUG

---
spring:
  config:
    activate:
      on-profile: prod
server:
  port: 80
logging:
  level:
    root: WARN

# application.properties
spring.profiles.active=dev
#---
spring.config.activate.on-profile=dev
server.port=8080
logging.level.root=DEBUG
#---
spring.config.activate.on-profile=prod
server.port=80
logging.level.root=WARN

# application.properties - 리스트 표현
app.allowed-origins[0]=http://localhost:3000
app.allowed-origins[1]=http://localhost:8080
app.allowed-origins[2]=https://example.com

app.security.roles[0].name=ADMIN
app.security.roles[0].permissions[0]=READ
app.security.roles[0].permissions[1]=WRITE
app.security.roles[0].permissions[2]=DELETE
app.security.roles[1].name=USER
app.security.roles[1].permissions[0]=READ

# application.yml - 리스트 표현
app:
  allowed-origins:
    - http://localhost:3000
    - http://localhost:8080
    - https://example.com

  security:
    roles:
      - name: ADMIN
        permissions:
          - READ
          - WRITE
          - DELETE
      - name: USER
        permissions:
          - READ

import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.stereotype.Component;
import java.util.List;

@Component
@ConfigurationProperties(prefix = "app")
public class AppProperties {

    private List<String> allowedOrigins;
    private Security security;

    public static class Security {
        private List<Role> roles;

        public static class Role {
            private String name;
            private List<String> permissions;

            // Getters and Setters
            public String getName() { return name; }
            public void setName(String name) { this.name = name; }
            public List<String> getPermissions() { return permissions; }
            public void setPermissions(List<String> permissions) { 
                this.permissions = permissions; 
            }
        }

        // Getters and Setters
        public List<Role> getRoles() { return roles; }
        public void setRoles(List<Role> roles) { this.roles = roles; }
    }

    // Getters and Setters
    public List<String> getAllowedOrigins() { return allowedOrigins; }
    public void setAllowedOrigins(List<String> allowedOrigins) { 
        this.allowedOrigins = allowedOrigins; 
    }
    public Security getSecurity() { return security; }
    public void setSecurity(Security security) { this.security = security; }
}

# application.properties
spring.datasource.url=${DATABASE_URL:jdbc:postgresql://localhost:5432/defaultdb}
spring.datasource.username=${DB_USER:root}
spring.datasource.password=${DB_PASSWORD}

app.api-key=${API_KEY:}
app.feature.enabled=${FEATURE_FLAG:false}

# application.yml
spring:
  datasource:
    url: ${DATABASE_URL:jdbc:postgresql://localhost:5432/defaultdb}
    username: ${DB_USER:root}
    password: ${DB_PASSWORD}

app:
  api-key: ${API_KEY:}
  feature:
    enabled: ${FEATURE_FLAG:false}

# application.yml - 임포트 기능
spring:
  config:
    import:
      - optional:file:./config/external.yml
      - optional:configserver:http://config-server:8888
      - classpath:additional-config.yml

---
spring:
  config:
    activate:
      on-cloud-platform: kubernetes
    import:
      - optional:configtree:/etc/config/

import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.context.properties.bind.ConstructorBinding;
import java.util.List;

@ConfigurationProperties(prefix = "app.mail")
public record MailProperties(
    String host,
    int port,
    String username,
    String password,
    List<String> recipients
) {
    public MailProperties {
        if (port <= 0 || port > 65535) {
            throw new IllegalArgumentException("Invalid port number");
        }
    }
}

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.context.properties.ConfigurationPropertiesScan;

@SpringBootApplication
@ConfigurationPropertiesScan
public class Application {

    public static void main(String[] args) {
        long startTime = System.currentTimeMillis();
        SpringApplication.run(Application.class, args);
        long endTime = System.currentTimeMillis();
        System.out.println("Startup time: " + (endTime - startTime) + "ms");
    }
}

import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

@Component
public class ValueExample {
    
    @Value("${app.name}")
    private String appName;
    
    @Value("${app.timeout:5000}")
    private int timeout;
    
    @Value("#{${app.map}}")
    private Map<String, String> configMap;
}

# application.yml - reference environment variable
spring:
  datasource:
    password: ${DB_PASSWORD}

# application.properties
spring.datasource.password=ENC(nrmZtkF7T0kjG/VodDvBw93Ct8EgjCA+)

# The master password is supplied at runtime, never committed
java -Djasypt.encryptor.password=$JASYPT_MASTER_KEY -jar app.jar

# application.yml - 공통 설정만
spring:
  application:
    name: my-service
  profiles:
    active: ${SPRING_PROFILES_ACTIVE:dev}

# 민감 정보는 환경 변수에서 가져오기
spring:
  datasource:
    password: ${DB_PASSWORD}

app:
  jwt:
    secret: ${JWT_SECRET}

import jakarta.validation.constraints.NotBlank;
import jakarta.validation.constraints.Positive;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.validation.annotation.Validated;

@Validated
@ConfigurationProperties(prefix = "app")
public class ValidatedAppProperties {

    @NotBlank(message = "Application name is required")
    private String name;

    @Positive(message = "Timeout must be positive")
    private int timeout;

    // Getters and Setters
    public String getName() { return name; }
    public void setName(String name) { this.name = name; }
    public int getTimeout() { return timeout; }
    public void setTimeout(int timeout) { this.timeout = timeout; }
}