Spring Boot Environment-specific configurations

Question

I have a spring boot application that uses the actuator, auto-configuration and JPA. I want to be able to use an in-memory DB in my test profile, a MySQL DB configuration during development and a separate production DB configuration when the app is deployed in production. Presumably from the java command line I should be able to specify the environment and the right configuration file or config block in application.properties (or .yml) will be picked up.

I have not found a good post with example describing how to do this switching so I thought I'd ask if anyone has a good example. My main aim is to pre-define the spring.datasource and spring.jpa properties at build time and then at run-time switch the app config per environment "dynamically" using the java command line argument. Secondary goal would be to do the same with the management configurations, etc.

Thank you.

Answer 1

Thanks to @Richard for the mention of spring.profiles.active JVM variable. Since my question was specific to the way Spring Boot does this and since there is much more to the answer, I am inclined to answer this myself and include all the details of how I arrived at the answer in the hopes that it will save others time.

First, you can indeed pick the correct profile on the java command line by adding -Dspring.profiles.active=profile_name when you are running your Spring Boot app. (this is assuming your deployment preference is an uber jar with embedded container - Tomcat in my case)

I wanted to leave MySQL datasource configurations under the default profile and put H2 in-memory datasource configuration under a test profile. However, the way Spring Boot picks the right datasource based on profile is not so obvious. Even though I had MySQL details under the default profile and I had the in-memory H2 datasource details under the test profile, it would still pick H2 as the datasource even when spring.profiles.active was omitted from the command line. This was contrary to my assumption that default profile will be picked, well, by default :-)

I ended up having to put H2 configuration under the default profile and then create a local profile that included the MySQL datasource configuration. Here's what I ended up with in my application.yml

spring:
  profiles: default 

spring:
  datasource:
    driverClassName: org.h2.Driver
    url: jdbc:h2:mem:sampletest;MODE=MySQL

---
spring:
  profiles: test

spring.jpa:
    hibernate:
      ddl-auto: create-drop

---
spring:
  profiles: local

spring.datasource:
  driverClassName: com.mysql.jdbc.Driver
  url: jdbc:mysql://127.0.0.1/sampledev
  username: sample
  password: sample

spring.jpa:
  hibernate:
    dialect: org.hibernate.dialect.MySQLInnoDBDialect
    ddl-auto: update

This worked. I was able to switch between default profiles and the local profile by omitting or adding the -Dspring.profiles.active=local on the java command line. Because test profile inherits from default it is also using H2

One more nuance: I added ddl-auto: create-drop to the test profile which uses the in-memory DB to facilitate automatic table creation / teardown for unit tests. But for the local profile which uses MySQL I changed it to update. Implication being that for the local profile I have to first create the database outside of the application.