application.properties & YAML

Introduction

application.properties and application.yml are interchangeable formats for Spring Boot configuration. YAML is preferred in modern projects: nested, less repetition, supports lists.

Syntax reference

# application.yml — same thing, nested
server:
  port: 8080
spring:
  datasource:
    url: jdbc:postgresql://localhost:5432/orders
  jpa:
    hibernate:
      ddl-auto: validate
logging:
  level:
    com.acme: DEBUG

Informative example

The same config in both formats:

# application.properties
server.port=8080
spring.datasource.url=jdbc:postgresql://localhost:5432/orders
spring.jpa.hibernate.ddl-auto=validate
logging.level.com.acme=DEBUG

Best practices

• Pick one format per project; mixing causes confusion.
• Per-env overrides: application-prod.yml activated by SPRING_PROFILES_ACTIVE=prod.
• Reference env vars: password: ${DB_PASSWORD}.