Webservice protocols

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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)