apollo-client/src/main/java/com/ctrip/framework/apollo/spring/property/SpringValueRegistry.java/SpringValueRegistry/register
class SpringValueRegistry:  public void register(BeanFactory beanFactory, String key, SpringValue springValue) {
    if (!registry.containsKey(beanFactory)) {
      synchronized (LOCK) {
        if (!registry.containsKey(beanFactory)) {
          registry.put(beanFactory, Multimaps.synchronizedListMultimap(LinkedListMultimap.<String, SpringValue>create()));
        }
      }
    }

    registry.get(beanFactory).put(key, springValue);

    // lazy initialize
    if (initialized.compareAndSet(false, true)) {
      initialize();
    }
  }