Java on Raspberry Pi

The “Pi” in the name of the Raspberry Pi refers to Python, but as a Java developer I love to know and experiment with the various Java frameworks I also use at work. Spring is the main one, and I wanted to develop a proof-of-concept application which provides REST API’s to store and retrieve sensor data with a database back-end on the Raspberry Pi.

In my book “Getting Started with Java on Raspberry Pi” I dedicated a chapter on Pi4J, the leading framework to combine the power of Java with the hardware capabilities of the Raspberry Pi. This project which was started in 2012 by Robert Savage, evolved during the years to be able to support all the different Raspberry Pi-versions and many types of hardware components.

In “The MagPi Magazine” #93 and #94, published by the Raspberry Pi Foundation, you can find two articles which describe how you can get started with Java, Maven, Visual Studio Code and Pi4J on the Raspberry Pi.

FXGL is a Java, JavaFX and Kotlin Game Library (Engine) made by Almas Baimagambetov. As my son (almost 10y) challenged me to make a game during my “Corona-stay-at-home-time”, I had the luck Almas provided me a getting-started with this detailed step-by-step.

One of the most read articles on this blog is about the installation of a recent Java on Raspberry Pi (March 13, 2019), so it’s time for an update!

Based on multiple examples from my book “Getting started with Java on Raspberry Pi”, I created a touchscreen controller for the drum booth of my son. Combined with relays boards and an Arduino this allows to control LED strips and different lights with a touch screen interface.

While looking for a cheap and nice component to demonstrate the use of SPI (Serial Peripheral Interface) I found out this 8x8 matrix LED display on a board with a MAX7219 chip is the perfect piece of hardware!

Pi4J contains helper methods to minimize the work needed to use certain hardware modules on the Pi with Java. As an example, we will be using “GpioLcdDisplay” to control an LCD with 2 rows of 16 characters. After requesting the weather forecast from a public website, we will visualize this on the LCD display.

Trisha Gee (Coder, blogger, speaker, Developer Advocate at JetBrains, @trisha_gee), which I interviewed for “Chapter 4: Choosing an IDE”, and Josh Long (Spring Developer Advocate at Pivotal, @starbuxman) worked together on a blog series in which they showed the power of reactive data produced by a Spring application. Instead of repeating a REST call each time you want to get data from the server, you do one call which returns a continuous stream in which new data is pushed based on an interval.

In my book I explain the use of bits and bytes by using a shift register SN74HC595 IC and 5101AS LED number display.