Building a Multipurpose IoT Controller

Raspberry Pi is great for building powerful server-based applications, configuring it to act as a web server by installing a web server such as Nginx, Apache, Jetty, or lighttpd. A web server can serve a web application to many users concurrently through a network. But unlike other traditional web applications, Raspberry Pi-hosted web applications can be used to interact with the Raspberry Pi itself, and other peripherals attached to it.

The following diagram shows a Raspberry Pi board configured as a web server with two clients connected to it through a router:

Figure 6-1: Simple Raspberry Pi client-server model

A lightweight web application can be used to interact with sensors and actuators attached to the Raspberry Pi. As an example, you could control an LED attached to a GPIO pin or display readings of a sensor attached to the I2C pins of the Raspberry Pi.

In this chapter...

Prerequisites

To build the series of projects that will be present in this chapter, you will need following things in your tool box:

Raspberry Pi 3 board
3 mm LED
220 Ohm resistor
Hookup wires

Preparing your Raspberry Pi board

Before going in too deep, let's prepare our Raspberry Pi board by installing the Jetty server for projects that will be discussed in this chapter.

Installing and configuring Jetty servelet engine

Jetty servlet engine is a lightweight server component that can be used to host web applications. Jetty servlet engine consumes less memory than an Apache server and it is great for saving resources on the Raspberry Pi.

You can learn more about Jetty by visiting http://www.eclipse.org/jetty/. It includes documentation, downloads, a Maven plugin, Eclipse tooling, mailing lists, Javadocs, tools, blogs, and much more that can help you to learn to use Jetty in your projects.

The following steps will guide you through installing and configuring...

Writing your first Java web application

The servlet you will be writing to control the Raspberry Pi's GPIO pin through the internet or any local area network requires a series of configurations to build and test in the Windows environment. Then you will deploy the project to the Raspberry Pi manually and run it on the Jetty server.

Creating a Maven project from Archetype

Open the NetBeans IDE and from the menu bar, click on File | New Project. The New Project wizard will appear.
In Choose Project (step 1), select Maven under Categoriesand Project from Archetype under Projects,as shown in Figure 6-4.
Then, click the Next button to proceed:

Figure 6-4: Choose project

In Maven Archetype (step 2), select maven-archetype-webapp under Known Archetypes, as shown...

Summary

In this chapter, you learned how to develop a Java web application with NetBeans to control a GPIO-connected LED through the network. You followed s series of steps to install and configure s Jetty server on both NetBeans and the Raspberry Pi. Finally, you deployed the web application, which is the .war file generated by the build process, to the Jetty server running on the Raspberry Pi.

The Chapter 7, Security Camera with Face Recognition, presents how to use OpenCV and Java with the Raspberry Pi to develop a video application with face recognition that can be used to build a security camera.