apollo-client/src/main/java/com/ctrip/framework/apollo/spring/config/PropertySourcesProcessor.java/PropertySourcesProcessor/setEnvironment
class PropertySourcesProcessor:  @Override
  public void setEnvironment(Environment environment) {
    //it is safe enough to cast as all known environment is derived from ConfigurableEnvironment
    this.environment = (ConfigurableEnvironment) environment;
  }