apollo-client/src/main/java/com/ctrip/framework/apollo/spring/boot/ApolloApplicationContextInitializer.java/ApolloApplicationContextInitializer/initializeSystemProperty
class ApolloApplicationContextInitializer:  void initializeSystemProperty(ConfigurableEnvironment environment) {
    for (String propertyName : APOLLO_SYSTEM_PROPERTIES) {
      fillSystemPropertyFromEnvironment(environment, propertyName);
    }
  }