Spring Boot: environment profiling for production and development?

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Accepted Answer

**Environment profiling** — configuring the application **separately for development, testing, and production**.

**Simple analogy:** Like a Swiss Army knife. One button opens the blade (dev), another opens the saw (prod). One tool — different modes. Or think of it like clothes: you wear pajamas at home (dev), casual clothes at a coffee shop (test), and a suit at work (prod). Same person, different outfits for different situations.

**Why it matters:** Running your production database credentials in development, or having DEBUG logging in production, are two common disasters. Profiles prevent these by keeping configurations isolated. Your dev team can see verbose SQL logs and use fake email senders, while production runs with tight security, optimized connection pools, and minimal logging.

**application.yml (common):**
```yaml
spring:
  profiles:
    active: dev
  application:
    name: my-app
```

**application-dev.yml:**
```yaml
spring:
  datasource:
    url: jdbc:postgresql://localhost:5432/devdb
    username: dev_user
    password: dev_password
  jpa:
    show-sql: true
    hibernate:
      ddl-auto: create-drop
logging:
  level:
    root: DEBUG
    com.example: TRACE
management:
  endpoints:
    web:
      exposure:
        include: "*"  # All endpoints in dev
```

**application-prod.yml:**
```yaml
spring:
  datasource:
    url: jdbc:postgresql://${DB_HOST}:5432/proddb
    hikari:
      maximum-pool-size: 20
      minimum-idle: 5
      connection-timeout: 30000
      idle-timeout: 600000
  jpa:
    show-sql: false
    hibernate:
      ddl-auto: validate
logging:
  level:
    root: WARN
    com.example: INFO
management:
  endpoints:
    web:
      exposure:
        include: health,info,metrics
  metrics:
    export:
      prometheus:
        enabled: true
```

**application-test.yml:**
```yaml
spring:
  datasource:
    url: jdbc:h2:mem:testdb
  jpa:
    hibernate:
      ddl-auto: create-drop
  mail:
    host: localhost
    port: 1025  # Mailhog or similar
```

**Programmatic beans by profile:**
```java
@Configuration
public class BeansConfig {
    @Bean
    @Profile("dev")
    public MailSender devMailSender() { return new FakeMailSender(); }

@Bean
    @Profile("prod")
    public MailSender prodMailSender() { return new SmtpMailSender(host, port); }
    
    @Bean
    @Profile("!prod")
    public Clock testClock() {
        return Clock.fixed(Instant.parse("2024-01-15T00:00:00Z"), ZoneId.of("UTC"));
    }
}
```

**Environment Variables (12-factor app):**
```bash
SPRING_PROFILES_ACTIVE=prod java -jar app.jar
SPRING_DATASOURCE_URL=jdbc:postgresql://... java -jar app.jar
```

**Common mistakes:**
- **Putting secrets in YAML files** — use environment variables or a vault (HashiCorp Vault, AWS Secrets Manager) instead.
- **Using `ddl-auto: update` in production** — Hibernate migrations can corrupt data. Use Flyway or Liquibase for controlled schema evolution.
- **Forgetting to activate the profile** — the app falls back to defaults which may point to localhost. Always verify with `spring.profiles.active`.
- **Profile-specific beans not loading** — `@Profile("prod")` means the bean only loads when the "prod" profile is active. If you run with no profile, it is ignored.

Java: Spring Boot: environment profiling for production and development?