YAML Configuration

How to Activate Profiles

From application.yml

spring:
  profiles:
    active: dev

From CLI

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

From environment variable

export SPRING_PROFILES_ACTIVE=test

From VSCode run config launch.json

"args": "--spring.profiles.active=dev",

From IDE run config

-Dspring.profiles.active=dev

Spring Boot YAML basic profile setup

A common base config (in application.yml)
Environment-specific profiles (application-dev.yml, application-test.yml, application-prod.yml)
Each profile extends the common configuration using spring.config.import

application.yml

# application.yml
spring:
  application:
    name: sample-app

  datasource:
    url: jdbc:mysql://localhost:3306/common_db
    username: common_user
    password: common_pass
    driver-class-name: com.mysql.cj.jdbc.Driver

server:
  port: 8080

logging:
  level:
    root: INFO
    com.example: INFO

application-dev.yml

# application-dev.yml

spring:
  config:
    import: application.yml

  datasource:
    url: jdbc:mysql://localhost:3306/dev_db
    username: dev_user
    password: dev_pass

server:
  port: 8081

logging:
  level:
    com.example: DEBUG

application-test.yml

# application-test.yml

spring:
  config:
    import: application.yml

spring:
  datasource:
    url: jdbc:h2:mem:test_db
    username: sa
    password:
    driver-class-name: org.h2.Driver

server:
  port: 8082

logging:
  level:
    com.example: TRACE

application-prod.yml

# application-prod.yml

spring:
  config:
    import: application.yml

spring:
  datasource:
    url: jdbc:mysql://prod-db:3306/prod_db
    username: ${DB_USER}
    password: ${DB_PASS}

server:
  port: 80

logging:
  level:
    root: WARN
    com.example: INFO

Spring Boot YAML advance profile setup

the complete, extended Spring Boot YAML configuration setup

Common config
Dev, Test, Production profiles
Property-map merging examples
Multiple import hierarchy
Secrets isolation (application-secrets.yml)
Full microservice-style config structure

application.yml

# application.yml
spring:
  application:
    name: sample-app

  profiles:
    active: dev  # default profile (can be overridden)

  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    username: common_user
    password: common_pass
    url: jdbc:mysql://localhost:3306/common_db

server:
  port: 8080

logging:
  level:
    root: INFO
    com.sample: INFO

app:
  name: Sample Application
  features:
    cache: false
    metrics: true

# Import secrets (not committed to Git)
spring:
  config:
    import: optional:application-secrets.yml

application-dev.yml

# application-dev.yml
spring:
  config:
    import:
      - application.yml
      - optional:application-secrets.yml

spring:
  datasource:
    url: jdbc:mysql://localhost:3306/dev_db
    username: dev_user
    password: dev_pass

server:
  port: 8081

logging:
  level:
    com.sample: DEBUG

app:
  features:
    cache: false  # override base
    debug-mode: true

application-test.yml

# application-test.yml
spring:
  config:
    import:
      - application.yml

spring:
  datasource:
    url: jdbc:h2:mem:test_db
    username: sa
    password:
    driver-class-name: org.h2.Driver

server:
  port: 8082

logging:
  level:
    com.sample: TRACE

app:
  features:
    cache: false
    metrics: false  # override for test

application-prod.yml

# application-prod.yml
spring:
  config:
    import:
      - application.yml
      - optional:application-secrets.yml

spring:
  datasource:
    url: jdbc:mysql://prod-db:3306/prod_db
    username: ${DB_USER}
    password: ${DB_PASS}

server:
  port: 80

logging:
  level:
    root: WARN
    com.sample: INFO

app:
  features:
    cache: true
    metrics: true
    audit: true

application-secrets.yml

⚠ Do NOT commit this file to Git. Put it in .gitignore.

# application-secrets.yml
spring:
  datasource:
    username: ${SECRET_DB_USER}
    password: ${SECRET_DB_PASS}

jwt:
  secret: ${JWT_SECRET_KEY}

api:
  key: ${EXTERNAL_API_KEY}

Multiple Import Hierarchy Example

A profile can import multiple layers:

application.yml  →  application-common.yml  →  application-dev.yml

application.yml

spring:
  config:
    import:
      - application-common.yml
      - optional:application-secrets.yml

application-common.yml:

server:
  forward-headers-strategy: framework
  error:
    include-stacktrace: on_param

application-dev.yml:

spring:
  config:
    import:
      - application.yml
      - optional:application-secrets.yml

debug: true

Property Map Merging Example

Base file:

app:
  mail:
    host: smtp.example.com
    ports:
      - 587
      - 465

Dev override (adds new port, merges list):

app:
  mail:
    ports:
      - 2525

Merged output during runtime:

app.mail.ports = [587, 465, 2525]

Microservice-Friendly Structure (Recommended)

config/
 ├── application.yml
 ├── application-common.yml
 ├── application-dev.yml
 ├── application-test.yml
 ├── application-prod.yml
 ├── application-secrets.yml
 └── application-monitoring.yml

Example application-monitoring.yml:

management:
  endpoints:
    web:
      exposure:
        include: health,info,prometheus
  metrics:
    export:
      prometheus:
        enabled: true

Imported from prod:

spring:
  config:
    import:
      - application.yml
      - application-monitoring.yml
      - optional:application-secrets.yml

Spring Boot YAML cloud profile setup

complete version of the Spring Boot configuration using Spring Cloud Config Server,

Config Server setup
Externalized YAML files in a Git repo
Client-side bootstrap config
Profiles (dev, test, prod)
Shared/common config
Secrets file
Hierarchical imports

✔ Only configuration files ✔ No Java code

Config Server

This file lives in the Config Server JAR (not the client apps).

# Config Server: application.yml
server:
  port: 8888

spring:
  application:
    name: config-server

  cloud:
    config:
      server:
        git:
          uri: https://github.com/your-org/your-config-repo.git
          clone-on-start: true
          search-paths:
            - configs

Folder Structure in Git (Config Repo)

your-config-repo/
└── configs/
    ├── sample-app.yml
    ├── sample-app-dev.yml
    ├── sample-app-test.yml
    ├── sample-app-prod.yml
    ├── sample-app-secrets.yml
    ├── sample-app-common.yml
    └── sample-app-monitoring.yml

These YAML files are fetched dynamically by Spring Cloud Config Clients.

Common Config

# sample-app.yml (default, shared for all profiles)
spring:
  application:
    name: sample-app

  datasource:
    url: jdbc:mysql://localhost:3306/common_db
    username: common_user
    password: common_pass
    driver-class-name: com.mysql.cj.jdbc.Driver

server:
  port: 8080

logging:
  level:
    root: INFO
    com.sample: INFO

app:
  features:
    metrics: true
    cache: false

spring:
  config:
    import:
      - optional:sample-app-common.yml
      - optional:sample-app-secrets.yml

Common Shared Config

# sample-app-common.yml
server:
  forward-headers-strategy: framework

management:
  endpoints:
    web:
      exposure:
        include: health,info

Secrets File

(Do NOT commit to public GitHub)

# sample-app-secrets.yml
spring:
  datasource:
    username: ${SECRET_DB_USER}
    password: ${SECRET_DB_PASS}

jwt:
  secret: ${JWT_SECRET_KEY}

Dev Profile

# sample-app-dev.yml
spring:
  config:
    import:
      - sample-app.yml
      - optional:sample-app-secrets.yml

spring:
  datasource:
    url: jdbc:mysql://localhost:3306/dev_db
    username: dev_user
    password: dev_pass

server:
  port: 8081

logging:
  level:
    com.sample: DEBUG

app:
  features:
    debug-mode: true
    cache: false

Test Profile

# sample-app-test.yml
spring:
  config:
    import:
      - sample-app.yml

spring:
  datasource:
    url: jdbc:h2:mem:test_db
    driver-class-name: org.h2.Driver
    username: sa
    password:

logging:
  level:
    com.sample: TRACE

server:
  port: 8082

app:
  features:
    metrics: false

Production Profile

# sample-app-prod.yml
spring:
  config:
    import:
      - sample-app.yml
      - optional:sample-app-secrets.yml
      - optional:sample-app-monitoring.yml

spring:
  datasource:
    url: jdbc:mysql://prod-db:3306/prod_db
    username: ${DB_USER}
    password: ${DB_PASS}

server:
  port: 80

logging:
  level:
    root: WARN
    com.sample: INFO

app:
  features:
    metrics: true
    audit: true
    cache: true

Monitoring Add-on File

# sample-app-monitoring.yml
management:
  endpoints:
    web:
      exposure:
        include: health,info,prometheus

management:
  metrics:
    export:
      prometheus:
        enabled: true

Client App

Every client application needs this file to load config from the Config Server.

# bootstrap.yml (client app)
spring:
  application:
    name: sample-app

  cloud:
    config:
      uri: http://localhost:8888
      fail-fast: true
      retry:
        max-attempts: 5
        initial-interval: 2000

# Optional: fallback local settings
spring:
  config:
    import:
      - optional:application-local.yml

Client App Profile Activation

Clients still use local profile activation, but config loads from server.

# application.yml (client app)
spring:
  profiles:
    active: dev

How Each Client App Loads Config

Example:

When profile = dev

Client fetches:

GET /sample-app/dev

Config from:

sample-app.yml
sample-app-dev.yml
sample-app-common.yml
sample-app-secrets.yml
(optional) monitoring file