Is there a way to control the output in the drupal services? Example, if a argument that is required, it not provided in the call, I get the following output as a JSON array.

Missing required argument title

I'd like to either override this output, or instead of returning a json object, just return plain text.

Is this possible to do?

1 Answer 1


You most certainly can.

If you open up the docs folder in the services module you can see the function hook_rest_server_execute_errors_alter(&$error_alter_array, $controller, $arguments) in the file services.alter.api.php

 * Allows alteration of error data before the status code or message are returned.
 * @param array $error_alter_array
 *   An associative array with the following keys:
 *     - 'code': the HTTP status code.
 *     - 'header_message': the message returned as part of the error response
 *       (for instance, "404 Not found").
 *     - 'body_data': data that was passed to the thrown exception.
 * @param array $controller
 *   The current controller definition.
 * @param array $arguments
 *   Arguments passed to the current controller.
 * @see RESTServer->handleException()
function hook_rest_server_execute_errors_alter(&$error_alter_array, $controller, $arguments) {


Example output would be:

Array (
  [code] => 401
  [header_message] => 401 Unauthorized : Missing required argument username
  [body_data] => Missing required argument username

So you could alter it like,

function MYMODULENAME_rest_server_execute_errors_alter(&$error_alter_array, $controller, $arguments) {
 $error_alter_array['code'] = 500;
 $error_alter_array['header_message'] = '500 Come on man, send that username';
 $error_alter_array['body_data'] = 'Come on man, send that username';

Note: You do not need to return anything because it is alter by reference and two, make sure you clear cache after adding this function to a module.

  • Feel free to upvote the answer too :) Oct 15, 2014 at 19:47

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