How to configure default application.properties via e.g. custom starter?

Question

To ease internal development I\'m thinking of developing a thin layer / customer starter for Spring Boot. This custom starter just depends on some boot starters and some oth

Answer 1

Spring Boot looks for properties using a specific order:

1. Command line arguments
2. Java System properties (System.getProperties())
3. OS environment variables
4. JNDI attributes from java:comp/env
5. A RandomValuePropertySource that only has properties in random.*
6. Application properties outside of your packaged jar (application.properties including YAML and profile variants)
7. Application properties packaged inside your jar (application.properties including YAML and profile variants)
8. @PropertySource annotations on your @Configuration classes
9. Default properties (specified using SpringApplication.setDefaultProperties)

To give the projects using your custom starter the most flexibility in how to override the defaults, you should use a mechanism that's as near to the end of the above list as possible. Given that you already have your own subclass of SpringApplication, I would use SpringApplication.setDefaultProperties(Properties) from within that subclass.