java/iot3mobility: fix topic root for mobility messages publication

[mathieu1fb]

Fixes;

IoT3 Mobility SDK: Fix topic root for CAM, DENM and CPM publication : it is now correctly set according to the "context" parameter.

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How to test

1. Clone the its-client project on your IDE.

2. Ensure that you have Gradle to be able to build the java/iot3 modules (core, mobility and examples).

3. Find the Iot3MobilityExample class in the examples module, and set appropriate values for the following fields:

   private static final String EXAMPLE_UUID = "uuid";
   private static final String EXAMPLE_CONTEXT = "context"; // this will be used as the topic root
   // MQTT parameters
   private static final String EXAMPLE_MQTT_HOST = "mqtt_host";
   private static final int EXAMPLE_MQTT_PORT = 1883;
   private static final String EXAMPLE_MQTT_USERNAME = "mqtt_username";
   private static final String EXAMPLE_MQTT_PASSWORD = "mqtt_password";
   private static final boolean EXAMPLE_MQTT_USE_TLS = false;

   Note: use an MQTT broker paired with an interQueue manager taking care of the inQueue -> outQueue copy.

4. Run Iot3MobilityExample and check that the mobility messages are published and received with the appropriate topic root (i.e. equal to the "context" parameter).

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Expected results:

1. CAMs should be sent and received at 1 Hz, and visible in the logs.
2. DENMs should be sent and received every 10 seconds, and visible in the logs.
3. CPMs should be sent and received at 1 Hz, and visible in the logs.

You can also use the ITSdroid app (with a project code matching the EXAMPLE_CONTEXT value), to visualise the messages at the UTAC TEQMO.

[mathieu1fb]

• [x] Code review OK

  • [x] Builds OK

  • [ ] Tests

Tests were not done, by lack of a way to run them from the command line; code changes are trivial enough that a code review was deemed enough to validate the change.

I will find a way to make it easily testable from a terminal in the next sprint.