Extends Drupal Services module to handle requests on node resource containing path alias instead of node id.

services_node_alias_to_system_path.info

name = Services Node Alias to System Path
description = Uses the Services API to convert requests containing a node path alias to a system path (e.g., 'node/5').
core = 7.x
version = 7.x-1.0

services_node_alias_to_system_path.module

<?php
/**
 * @file
 * Code for the Services Node Alias to System Path module.
 */

/**
 * Implements hook_services_resources_alter().
 *
 * In order to handle aliases with multiple parts (e.g. about/media), the 
 * string in the request should have slashes converted to triple dashes (---).
 */
function services_node_alias_to_system_path_services_resources_alter(&$resources, &$endpoint) {
  $args = array(
    'name' => 'alias',
    'optional' => FALSE,
    'source' => array('path' => 0),
    'type' => 'string',
    'description' => 'The alias node to get',
  );
  $resources['node']['operations']['retrieve']['args'] = array($args);
  $resources['node']['operations']['retrieve']['callback'] = '_services_node_alias_to_system_path_retrieve';
  $resources['node']['operations']['retrieve']['access callback'] = '_services_node_alias_to_system_path_node_resource_access';
  $resources['node']['operations']['retrieve']['access arguments append'] = TRUE;
}

function _services_node_alias_to_system_path_retrieve($alias){
  $nid = _services_node_alias_to_system_path_find_nid($alias);
  if ($nid) {
    return _node_resource_retrieve($nid);
  }
  return FALSE;
}

function _services_node_alias_to_system_path_node_resource_access($op, $alias) {
  $nid = _services_node_alias_to_system_path_find_nid($alias[0]);
  if ($nid) {
    return _node_resource_access($op, array($nid));
  }
  return services_error(t('Content could not be found.'), 404);
}

/**
 * Helper function.
 */
function _services_node_alias_to_system_path_find_nid($alias) {
  
  // Convert dashes to slashes.
  $alias = str_replace('---', '/', $alias);
  
  // Look up internal path. 
  $path = drupal_get_normal_path($alias);
  
  // If drupal_get_normal_path() returns the alias, equate this to FALSE (no
  // internal path available).
  $is_node = $path !== $alias;
  
  if ($is_node && ctype_digit($nid = str_replace('node/', '', $path))) {
    return $nid;
  }
  return FALSE;
}

@cavla Thanks for sharing!