apollo-client/src/main/java/com/ctrip/framework/apollo/spring/property/PlaceholderHelper.java/PlaceholderHelper/evaluateBeanDefinitionString
class PlaceholderHelper:  private Object evaluateBeanDefinitionString(ConfigurableBeanFactory beanFactory, String value,
      BeanDefinition beanDefinition) {
    if (beanFactory.getBeanExpressionResolver() == null) {
      return value;
    }
    Scope scope = (beanDefinition != null ? beanFactory
        .getRegisteredScope(beanDefinition.getScope()) : null);
    return beanFactory.getBeanExpressionResolver()
        .evaluate(value, new BeanExpressionContext(beanFactory, scope));
  }