Spring boot auto configuration with dependency and without @ComponentScan

Question

Spring boot provides @ComponentScan to find packages to be scanned.

I am building a library which has @RestControllers inside with package com

Answer 1

You could create a Spring Boot Starter in the same style as the Spring Provided Starters. They are essentially a jar'd library with a a spring.factories file pointing to the @Configuration class to load with some other annotations on there to provide overriding/bean back off (@ConditionalOnMissingBean) and generally provide their own @ConfigurationProperties.

Stéphane Nicoll provided an excellent demo of how to build one.

https://github.com/snicoll-demos/hello-service-auto-configuration

It is also documented in the Spring Boot documentation. https://docs.spring.io/spring-boot/docs/current/reference/html/boot-features-developing-auto-configuration.html

The library approach would also work but I see no benefit in not making it a starter. Additionally for any library/starter I'd recommend dropping the @ComponentScan and just defining the beans in a @Configuration. This will work for sterotypes like @RestController etc. will function as normal if you create an @Bean out of it in a configuration.