SpringBoot 内置的 EnvironmentPostProcessor，在接收到 ApplicationEnvironmentPreparedEvent 事件中被触发调用

1. SystemEnvironmentPropertySourceEnvironmentPostProcessor，包装系统环境变量，生成一份新的可提供一些追踪信息的 ProertySource
2. SpringApplicationJsonEnvironmentPostProcessor，从 PropertySource 中获取名为 spring.application.json 或者 SPRING_APPLICATION_JSON 的配置，将其解析为名为 spring.application.json 的 PropertySource，加入到 environment 当中
3. CloudFoundryVcapEnvironmentPostProcessor
4. HostInfoEnvironmentPostProcessor
5. ConfigFileApplicationListener，加载 classpath 下的 application/bootstrap(?-profile) 配置文件

SpringCloud 启动时，JsonProcessor 可获取到的 PropertySource 为

0 = {MapPropertySource@2105} ****"MapPropertySource {name='bootstrap'}"
1 = {MapPropertySource@2106} "MapPropertySource {name='systemProperties'}"
2 = {SystemEnvironmentPropertySourceEnvironmentPostProcessor$OriginAwareSystemEnvironmentPropertySource@2107} "OriginAwareSystemEnvironmentPropertySource {name='systemEnvironment'}"

SpringBoot 启动时，JsonProcessor 可获取到的 PropertySource 为

0 = {MapPropertySource@2106} "MapPropertySource {name='systemProperties'}"
1 = {SystemEnvironmentPropertySourceEnvironmentPostProcessor$OriginAwareSystemEnvironmentPropertySource@4050} "OriginAwareSystemEnvironmentPropertySource {name='systemEnvironment'}"
2 = {BootstrapApplicationListener$ExtendedDefaultPropertySource@4051} "ExtendedDefaultPropertySource {name='defaultProperties'}"
sources = {CompositePropertySource@4061} "CompositePropertySource {name='defaultProperties', propertySources=[OriginTrackedMapPropertySource {name='applicationConfig: [classpath:/bootstrap-dev.yml]'}, OriginTrackedMapPropertySource {name='applicationConfig: [classpath:/bootstrap.yml]'}]}"
、

1-3 由 Devtool 或者测试实现类完成（在调用 SpringApplication#run 前置入）

4 由 SpringApplication#prepareEnvironment#configurePropertySources

5 由 SpringApplicationJsonEnvironmentPostProcessor 处理，优先级高于 command line

6-10，17 在创建时设置，其中 6,7 Servlet 相关在 Servlet 环境加载前是 Stub 状态（非可用），见 SpringApplication#prepareEnvironment#configureEnvironment

ConfigFileApplicationListener#postProcessEnvironment 处理 配置优先级 11-15

16 在解析 Bean 定义期间处理，如果发现 beanDefination 是注解类型，会调用 ConfigurationClassParser 进行处理，实际委托给了 DefaultPropertySourceFactory#createPropertySource 处理

配置优先级

spring boot 优先级

1. Devtools global settings properties on your home directory (~/.spring-boot-
devtools.properties when devtools is active).
2. @TestPropertySource annotations on your tests.
3. @SpringBootTest#properties annotation attribute on your tests.
4. Command line arguments.
5. Properties from SPRING_APPLICATION_JSON (inline JSON embedded in an environment variable
or system property).
6. ServletConfig init parameters.
7. ServletContext init parameters.
8. JNDI attributes from java:comp/env.
9. Java System properties (System.getProperties()).
10. OS environment variables.
11. A RandomValuePropertySource that has properties only in random.*.
12. Profile-specific application properties outside of your packaged jar (application-
{profile}.properties and YAML variants).
13. Profile-specific application properties packaged inside your jar (application-
{profile}.properties and YAML variants).
14. Application properties outside of your packaged jar (application.properties and YAML
variants).
15. Application properties packaged inside your jar (application.properties and YAML variants).
16. @PropertySource annotations on your @Configuration classes.
17. Default properties (specified by setting SpringApplication.setDefaultProperties).

spring cloud 控制代码逻辑