Webservice protocols

Introduction

Web service protocol plugins are web service servers. These servers let external applications call Moodle web service functions in an specific protocol: REST / AMF / SOAP /XML-RPC / ...

Examples

The easiest example is the REST server.

File structure

webservice/myprotocol/db/access.php

You must define the protocol capability here. To use the protocol, users must have this capability on system context. <?php

/**

* myprotocol server related capabilities
*
* @package    webservice_myprotocol
* @category   access
* @copyright  20XX Your Name
* @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
*/

$capabilities = array(

   'webservice/myprotocol:use' => array(
       'riskbitmask' => RISK_CONFIG | RISK_DATALOSS | RISK_SPAM | RISK_PERSONAL | RISK_XSS,
       'captype' => 'read', // in fact this may be considered read and write at the same time
       'contextlevel' => CONTEXT_COURSE, // the context level should be probably CONTEXT_MODULE
       'archetypes' => array(
       ),
   ),

);

webservice/myprotocol/lang/en/webservice_myprotocol.php

<?php

/**

* Strings for component 'webservice_myprotocol', language 'en', branch 'MOODLE_XX_STABLE'
*
* @package    webservice_myprotocol
* @category   string
* @copyright  20XX Your Name
* @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
*/

$string['pluginname'] = 'myprotocol protocol'; $string['myprotocol:use'] = 'Use myprotocol protocol';

webservice/myprotocol/server.php

This is the entry point of your server. The web service clients will call this file with the web service function name/parameters and the web service token. In this file you could want to catch some other $_REQUEST parameters as the REST server does. But it's most likely that very few changes are going to be done here. <?php /**

* myprotocol web service entry point. The authentication is done via tokens.
*
* @package    webservice_myprotocol
* @copyright  20XX Your Name
* @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
*/

/**

* NO_DEBUG_DISPLAY - disable moodle specific debug messages and any errors in output
*/

define('NO_DEBUG_DISPLAY', true);

/**

* NO_MOODLE_COOKIES - no cookies with web service
*/

define('NO_MOODLE_COOKIES', true);

require('../../config.php'); require_once("$CFG->dirroot/webservice/myprotocol/locallib.php");

if (!webservice_protocol_is_enabled('myprotocol')) {

   die;

}

$server = new webservice_rest_server(WEBSERVICE_AUTHMETHOD_PERMANENT_TOKEN); $server->run(); die;

webservice/myprotocol/locallib.php

That's where all the magic happens. Have a look how the REST server or the Zend servers extend webservice_base_server.

<?php

/**

* myprotocol web service implementation classes and methods.
*
* @package    webservice_myprotocol
* @copyright  20XX Your Name
* @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
*/

require_once("$CFG->dirroot/webservice/lib.php");

/**

* myprotocol service server implementation.
*
* @package    webservice_myprotocol
* @copyright  20XX Your Name
* @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
*/

class webservice_myprotocol_server extends webservice_base_server {

   /**
    * Contructor
    *
    * @param string $authmethod authentication method of the web service (WEBSERVICE_AUTHMETHOD_PERMANENT_TOKEN, ...)
    */
   public function __construct($authmethod) {
       parent::__construct($authmethod);
   }

   /**
    * This method parses the $_REQUEST
    */
   protected function parse_request() {
      //Retrieve the user credentials (token / ...), the web service function parameters, ...
      $this->token = isset($_REQUEST['wstoken']) ? $_REQUEST['wstoken'] : null;
      unset($_REQUEST['wstoken']);

      $this->functionname = isset($_REQUEST['wsfunction']) ? $_REQUEST['wsfunction'] : null;
      unset($_REQUEST['wsfunction']);

      $this->parameters = $_REQUEST;
   }

   /**
    * Send the result of function call to the WS client
    */
   protected function send_response() {

       // Check that the returned values are valid
       // sometimes it is not necessary like for Zend servers where 
       // the cleaning is done in service_class_method_body() of the webservice_zend_server class
       try {
           $validatedvalues = external_api::clean_returnvalue($this->function->returns_desc, $this->returns);
       } catch (Exception $ex) {
           $exception = $ex;
       }

       //PROCESS THE RESPONSE
       echo $response;
   }

   /**
    * Send the error information to the WS client
    * @param exception $ex the exception that we are sending
    */
   protected function send_error($ex=null) {
       //PROCESS THE ERROR MESSAGE
       echo $error;
   }

}

webservice/myprotocol/version.php

<?php

/**

* Version details
*
* @package    webservice_myprotocol
* @copyright  20XX Your Name
* @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
*/

defined('MOODLE_INTERNAL') || die();

$plugin->version = YYYYMMDDXX; // The current plugin version (Date: YYYYMMDDXX) $plugin->requires = yyyymmddxx; // Requires this Moodle version $plugin->component = 'webservice_myprotocol'; // Full name of the plugin (used for diagnostics)