This project is a simple example of using Apache Cassandra and Javalin to build a high-performance asynchronous REST server.
The project is presently using the Apache Cassandra 3.x driver. The 4.x driver has significant improvements that remove the need for the asynchronous boilerplate code in WidgetDao (most notably natively working with CompletableFuture rather than Guava's ListenableFuture and better built in support for asynchronous paging), however it has yet to be release as of the time of this writing.
The simplicity of Javalin is very evident in this Java project, however much of the Javalin framework is even more impressive when usin Kotlin. The intent of this project was to demonstrate the asynchronous interactions between Cassandra and Javalin in Java, however I'm also working on an example project using Cassandra and Javalin in Kotlin.
The portion of the project that leverages Cassandra is in the WidgetDao and the portion of the project that leverages Javalin is in the ExampleApp.
There is also an example E2E test available in the ExampleAppE2ETest, that extends the E2ETestBase class, which is responsible for starting the Javalin webserver in a background thread for E2E tests.
My name is Ben Christenson and I am the Tech Lead (meaning that I am responsible for a combination of architecture, development, and team leadership) at Kinetic Data. I'm heavily involved with 3 platform components heavily leveraging Cassandra and 2 components exposed via Javalin (one high performance REST API and one that exposes platform events via Websockets).
Cassandra is a prerequisite for running the sample app and E2E test case. Comprehensive instructions for installation and configuration of Cassandra is out of scope for this project, but a bare-bones example installation process is included below.
Example installation (OSX):
mkdir ~/servers
cd ~/servers
wget https://www-us.apache.org/dist/cassandra/3.11.3/apache-cassandra-3.11.3-bin.tar.gz
tar xf apache-cassandra-3.11.3-bin.tar.gz
cd apache-cassandra-3.11.3/bin
./cassandra
Copy and past the following into CQLSH ($ ~/servers/apache-cassandra-3.11.3/bin/cqlsh):
CREATE KEYSPACE IF NOT EXISTS cassandra_javalin_example
WITH REPLICATION = { 'class' : 'SimpleStrategy', 'replication_factor' : 1 };
USE cassandra_javalin_example;
CREATE TABLE IF NOT EXISTS widgets (
tenant_key text,
key text,
description text,
PRIMARY KEY ((tenant_key), key)
);