USSD (WIP)

Introduction

Helium and the Helium DSL provides built-in functionality for USSD integration. The DSL provides an interface for these integrations through a USSD annotation and MezUssdMenu and MezUssdMenuOption built-in objects.

Functions that are annotated with @USSD serve as integration endpoints that are available to be executed for inbound requests from USSD gateways. These functions then return an instance of MezUssdMenu that describes the next menu structure that is to be presented to the end user during his USSD session.

Overview

The basis of integrating with a USSD gateway is through calls from the USSD gateway to Helium.

When a user initiates a USSD session on the mobile device an API call is made to Helium's API. The calls are then routed to a specific @USSD annotated DSL function within an app. The app then response with the menu structure that is to be presented to the end user. Helium then translates this response as is required by the specific gateway.

@USSD

One of the following signatures is expected for USSD annotated functions:

@USSD("description")
MezUssdMenu processUssd(int menu, int selection)

@USSD("description")
MezUssdMenu processUssd(int menu, int selection, json gatewayArgs)

The purpose of the provided parameters are as follows:

menu:

An integer that indicates the menu from which the USSD request originated. For an initial call a value of 0 is sent.

selection:

An integer that indicates the menu option that was selected for the current request. For an initial call a value of 0 is sent.

gatewayArgs:

A json parameter that is populated with all additional query parameters sent by the gateway to Helium. At present the only gateway that is supported is Vodacom USSD gateway. The following shows an example of values that are sent for this gateway:

{
    "msisdn":"27763303624",
    "request":"*120*247253#",
    "provider":"Vodacom",
    "ussdSessionId":"2496158596"
}

The json attributes listed in the above example represent to following:

MezUssdMenu and MezUssdMenuOption