apollo-client/src/main/java/com/ctrip/framework/apollo/spring/spi/DefaultApolloConfigRegistrarHelper.java/DefaultApolloConfigRegistrarHelper/resolveNamespaces
class DefaultApolloConfigRegistrarHelper:  private String[] resolveNamespaces(String[] namespaces) {
    // no support for Spring version prior to 3.2.x, see https://github.com/apolloconfig/apollo/issues/4178
    if (this.environment == null) {
      logNamespacePlaceholderNotSupportedMessage(namespaces);
      return namespaces;
    }
    String[] resolvedNamespaces = new String[namespaces.length];
    for (int i = 0; i < namespaces.length; i++) {
      // throw IllegalArgumentException if given text is null or if any placeholders are unresolvable
      resolvedNamespaces[i] = this.environment.resolveRequiredPlaceholders(namespaces[i]);
    }
    return resolvedNamespaces;
  }