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| {{Template:Work in progress}}{{Moodle_2.0}} | | {{Template:Migrated|newDocId=/docs/apis/subsystems/external/}} |
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| =Introduction=
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| This page described the Web Services module implemented for Moodle 2.0<br>
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| The tracker issue is here: MDL-12886<br>
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| This module is been implemented by the [http://blogs.dfwikilabs.org/moodle_ws/ DFWS Team] and Moodle.
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| =Implementation=
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| Web Services module has been conceived in a purpose to be ported on different Moodle version, and also on different project. It has also for purpose to support multiple web service protocols (REST, SOAP, AMF, ...). Adding a new protocol support should be relatively easy.
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| == How it works ==
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| #The client sends a username and password to the web service protocol server script.
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| #The protocol server returns a session token for that user account (how this is sent depends on the protocol).
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| #The client calls a particular web service function (module name, function name, and function parameters), including the session token.
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| #The protocol server uses the token to check that the session is still active.
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| #The protocol server call the matching external function, located in a external.php file inside the relevant module.
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| #The external function checks that the current user has_capability to do this operation.
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| #The external function calls the matching Moodle core function (in lib.php usually).
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| #The core function can return a result to the external function.
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| #The external function will return a result to the protocol server.
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| #The protocol server returns the result to the client.
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| [[Image:Web_service_graph.jpg]]
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| == Code example ==
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| Following some bits of code in order to explain the concept
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| ===REST_server.php===
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| <code php>
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| ///REST params conversion
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| $functionname = 'delete_user' //retrieve function name from the REST parameters
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| $modulename = 'user' //retrieve module name from the REST parameters
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| $classname = $modulename.'_external';
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| /// Authentication process
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| $token = ... //retrieve token from the REST parameters
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| if (empty($token)) {
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| if ($functionname != 'generate_token') {
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| throw new moodle_exception('mustidentifyfirst');
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| } else {
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| ///authentication + token generation
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| $username = ... //retrieve username from the REST parameters
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| $password = ... //retrieve password from the REST parameters
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| if ($token = generate_token($username,$password)) {
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| return $token;
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| } else {
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| throw new moodle_exception('wrongusernamepassword');
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| }
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| }
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| } else {
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| ///the client is already identified
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| $user = verify_token($token);
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| if (empty($user)) {
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| throw new moodle_exception('wrongidentification');
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| }
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| else {
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| ///Load the user in order to get its context
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| $USER = $user;
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| }
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| }
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| /// load the external class
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| require_once($CFG->dirroot.$apipath.'external.php');
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| $wsapi = new $classname();
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| $description = $wsapi->get_function_webservice_description($functionname); //retrieve the web service description for this function
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| /// retrieve all rest params in an array
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| $params = retrieve_rest_params ($description); //retrieve the REST params
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| /// call the web service function | |
| $result = call_user_func_array ( $classname.'::'.$functionname, array($params));
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|
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| /// Return the result to the client
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| echo convert_into_rest_format(result);
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| </code>
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| === external.php===
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| <code php>
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| final class user_external extends moodle_external {
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| /**
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| * Constructor - We set the description of this API in order to be access by Web service
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| */
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| function __construct () {
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| $this->descriptions = array();
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| ///The desciption of the web service
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| ///
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| ///'params', 'optionalparams' and 'return' are used to described the web services to the end user
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| ///(can build WSDL file from these information)
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| $this->descriptions['delete_user'] = array( 'params' => array('username'=> PARAM_ALPHANUM),
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| 'optionalparams' => array( ),
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| 'return' => array('result' => PARAM_BOOL));
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| /**
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| * Delete a user
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| * @global object $DB
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| * @param array $params
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| * ->username string
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| * @return boolean true if success
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| */
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| static function delete_user($params) {
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| global $DB,$USER;
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| $user = $DB->get_record('user', array('username'=>$params['username']));
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| if (has_capability('moodle/user:delete', get_context_instance(CONTEXT_SYSTEM))) {
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| return delete_user($user); //this core function is in moodlelib.php
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| }
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| else {
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| throw new moodle_exception('couldnotdeleteuser');
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| }
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| }
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| }
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| ?>
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| </code>
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| =List of functions=
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| All callable functions are declared into each external.php. A "description" array contains all function names, parameter names and types, and return type.
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| =Authentication=
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| In order to manage authentication we will create a Web Service authentication plugin. Every external system wanting to call a Moodle web service will need to know at least one web service user (login/password). The authentication plugin will be able to:
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| * enable protocol (SOAP, REST, AMF, XMLRPC, ...)
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| * configure protocol (if they can be configured)
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| * list web services users and configure them (I.P. whitelist, ...)
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| Note that a user is defined as a web service user is he has the "cancallwebservice" capability.
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