Spring Libraries Development Best Practice

[stliu]

Inspired by this and this

1. When create a new class, make it in implementation package by default, also non-public by default, as stated here

[chenrujun]

Bean definition best practice:

1. XxxConfiguratoin should put in implementation package. Because customer will not use these classes in their java code. We should expose public API as less as possible.
2. XxxAutoConfiguration should NOT put in implementation package. Because customer may use it like @SpringBootApplication(exclude=XxxAutoConfiguration.class).
3. spring.factories only contains XxxAutoConfiguration. It should not contain XxxConfiguration. If spring.factories contains XxxConfiguration, customer cannot exclude XxxConfiguration in their application. Because customer should not use the classes in implementation package. And Java 9's modules system can hide implementation package.
4. XxxAutoConfiguration should import XxxConfiguratoins, should not define bean directly. The bean definition is implementation detail. It should not expose as public API.

Question:

1. If XxxConfiguration put in implementation package, and Java 9's modules system hide implementation package, Can Spring create bean according to XxxConfiguration?

[chenrujun]

Moved this into the private wiki inside Spring Cloud Azure team. Because it's not ready to publish.