apollo-client/src/main/java/com/ctrip/framework/apollo/spring/property/SpringValue.java/SpringValue/toString
class SpringValue:  @Override
  public String toString() {
    Object bean = beanRef.get();
    if (bean == null) {
      return "";
    }
    if (isField()) {
      return String
          .format("key: %s, beanName: %s, field: %s.%s", key, beanName, bean.getClass().getName(), field.getName());
    }
    return String.format("key: %s, beanName: %s, method: %s.%s", key, beanName, bean.getClass().getName(),
        methodParameter.getMethod().getName());
  }