1. Running Our Robot Overlords with Jakarta EE
Experiments in Java Controlling the GoPiGo3 Robot Car
With
Ken Fogel

2. The Test Platform Dexter Industries GoPiGo3 Robot Car
Development PC (Win 10)
Wireless Router
TP-Link WR810N
8 AA batteries
(NIMH)
Ultrasonic Sensor for GrovePi
Optional servo motor for sensor sweep
Raspberry Pi Computer

3. The Workbench

4. Writing the Java Drivers
The only Java code available from Dexter turned on or off the motors
I had to chose from interpreting the Python code or the C code.
Found some code that would be at home in my talk about Java Villainy.
Kudos to the Pi4J project for providing the necessary code in its core library to communicate with the GoPiGo3 daughterboard
Writing the Java Drivers

5. The Java Developer’s Secret Weapon

6. Starting Point in Java
public void runMotor(int motor, int power) throws IOException { //TODO Create a Builder byte command[] = new byte[] { (byte) 8, // first byte, start bit (byte) 10, // SET_MOTOR_PWM (byte) motor, // 1 | 2 (byte) power, // }; this.spi.write(command); }

7. Creating a CDI Injectible GoPiGo3 Driver
GoPiGo3DriverProducer

8. Experiment #1: The Basic JSF Controller

9. Experiment #2: The Basic REST Service

10. Experiment #3: JSF 2.3 Websocket Push
JSF 2.3 supports websockets with a tag and a dash of JS
Annotations define the push method
As the Ultrasonic Sensor must continuously send a stream of data we need a Thread
Prior it Java EE 7 creating threads in server side objects was frowned upon
Java EE 7 introduced extensions to the SE ThreadFactory called the ManagedThreadFactory
Now threads can be created in EE objects
Experiment #3: JSF 2.3 Websocket Push

11. JSF 2.3 Websocket Endpoint
A new JSF tag
<f:websocket channel="distance" onmessage="socketListener" />
A little JavaScript
<script>
var reload = true;
function socketListener(message, channel, event) {
document.getElementById("distanceId").innerHTML = message; }
</script>
We now have an endpoint

12. Websocket Endpoint Web Page

13. Experiment #5: Websockets- SE to EE
Lots of confusion over the programmatic versus the annotation approach
The Oracle documentation is clear but minimal
The blogs less so
As I write this slide I can send messages to the car but can’t receive a reply
It could be working by the time of the presentation

14. Source Code https://gitlab.com/omniprof/gopigo33driver.git

15. Who am I?
Co-Chair & Co-Program Coordinator of the Computer Science Technology Program at Dawson College, Montreal
Instructor in the Computer Institute of Concordia University
Blogger at and on DZone
Frequent Twitterer on
Speaker at JavaOne from
Speaker at Code One in 2018
Speaker at ApacheCon in 2018
Organizer of DawsCon, free one day conference in Montreal on January 11, 2019