apollo-client/src/main/java/com/ctrip/framework/apollo/spring/property/PlaceholderHelper.java/PlaceholderHelper/isExpressionWithPlaceholder
class PlaceholderHelper:  private boolean isExpressionWithPlaceholder(String propertyString) {
    return propertyString.startsWith(EXPRESSION_PREFIX) && propertyString.contains(EXPRESSION_SUFFIX)
        && propertyString.contains(PLACEHOLDER_PREFIX) && propertyString.contains(PLACEHOLDER_SUFFIX);
  }