Development:Web services

Note: This article is a work in progress. Please use the page comments for any recommendations/suggestions for improvement.

Moodle 2.0

Introduction

This page described the Web Services module implemented for Moodle 2.0
The tracker issue is here: MDL-12886
This module is been implemented by the DFWS Team.

Implementation

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, AMFPHP, ...). Adding a new protocol support should be relatively easy.

How does it work

The web service client call a Moodle web service. The web service is located in a folder specific to the used protocol. It's usually a inout.php file. This file runs the web service server and gets the sent parameters. Then it calls a wrapper. The wrapper.php file is implemented in order to call the Moodle API which contains all callable functions. The wrapper will check a "generated file" in order to know which functions are available, and what their parameters and what they returned.
For any protocol there should be at least one inout.php file and one wrapper file.

Technical specs

1. The client calls the web service
2. The web service server receives the call
3. The web service server transforms the web service params into a common param format to all web service protocol => Format to be defined
4. The web service server calls a function call_moodle_function($functionname, $params)
5. call_moodle_function() checks through a WS API descriptor class that the params are legal for this function name
6. call_moodle_function() call the correct API moodle function
7. the call_moodle_function() return the result to the web service server
8. the web service server convert the result into a response

Params should include:

• function parameter names, values and types
• returned object fields (e.g. we cannot return a password field through a get_users function)
• return value and type

Security

How are the web services secured ?
Security layer implemented by every protocol?

List of functions

All callable functions are declared into Moodle API, please read Moodle API documentation.