Scala

Many developers were burned by the overly complex world of Java back in the early 2000s. The Gang of Four patterns and middleware / J2EE / Java EE led to ridiculous levels of alleged decoupling as is evident in this sequence diagram from an open source J2EE ecommerce system I worked on in 2002:

Back in 2014 I wrote about how things had changed: Java Doesn’t Suck – You’re Just Using it Wrong.  But six years have passed since I wrote that and things have continued to improve, making the Java platform a fantastic option when building microservices, data pipelines, web apps, mobile apps, and more.  Let’s walk through some of the “modern” (as of 2021) aspects to the Java platform.

There comes a point in every Functional Programmer’s life where they feel the curse of the Monad has lifted and they must now explain Monads to their friends who just don’t get it. What follows is probably wrong and confusing, cause there is no escaping the curse. But here goes…

Suppose you have a system property that contains the name of another system property, like:

KEYNAME=FOO

And you want the value of FOO, like:

At first glance it seems silly to do batching in the reactive world. When I first started with reactive programming I thought I wouldn’t have to worry about things like resource starvation. After all, the reactive magic bullet was *magical*! But my magic bullet fizzled when it hit downstream resource constraints causing me to need batching.

With a reactive web client library like Play Framework’s, I can easily spin up tens of thousands of web requests, in parallel, using very little resources. But what if that saturates the server I’m making requests to? In an ideal world I could get backpressure but most web endpoints don’t provide a way to do that. So we just have to be nicer to the server and batch the requests. (Sidenote: How do you know how nice you should be to the service, e.g. batch size?)

Lately I’ve built a few apps that have relational data. Instead of trying to shoehorn that data into a NoSQL model I decided to use the awesome Heroku Postgres service but I didn’t want to lose out on the Reactiveness that most of the NoSQL data stores support. I discovered ScalikeJDBC-Async which uses postgresql-async, a Reactive (non-blocking), JDBC-ish, Postgres driver. With those libraries I was able to keep my data relational and my app Reactive all the way down. Lets walk through how to do it in a Play Framework app. (TL;DR: Jump to the the full source.)

This Wednesday (Aug 6, 2014) I will be presenting Building & Deploying Reactive Service Pipelines at the Utah Scala Enthusiasts group in Salt Lake City. Here is the abstract:

Composition of micro-service is a modern integration pattern that couples nicely with Reactive and Continuous Delivery. These paradigms enable small teams to move quickly while integrating cross-silo data stores for modern JavaScript UIs and REST services. This session will use Scala, Play Framework, and Heroku to illustrate how to build and deploy Reactive Service Pipelines.

This year at OSCON I will be leading a hands-on lab and presenting about Reactive, Play Framework, and Scala. Here are two sessions:

• Reactive All The Way Down (lab) - 9:00am Monday, July 21

  In this tutorial you will build a Reactive application with Play Framework, Scala, WebSockets, and AngularJS. We will get started with a template app in Typesafe Activator. Then we will add a Reactive RESTful JSON service and a WebSocket in Scala. We will then build the UI with AngularJS.

Bruce Eckel will be hosting the Scala Summit in Crested Butte again this summer. The Open Spaces conference will be September 15 - 19 which is a perfect time of year up in the Colorado Rockies. The theme of the Scala Summit this year is Scala vs. The New Features in Java 8. So there will definitely be some fascinating discussions. I’m also looking forward to working on some IoT projects during the hackathons. Bruce and I have a few pcDuino devices that will be fun to get Scala working on. Hope to see you there!

On Monday March 24th I will be co-presenting a Webinar about Scala and Vaadin. In this Webinar you will learn how to create great looking web UIs with Vaadin and Scala. No prior Scala experience is necessary. We will start with the basics. Hope to see you there!

At Devoxx 2013 Stephen Chin interviewed me on his NightHacking video podcast about Play Framework, Scala, and Reactive. Here is the recording with some live coding fun:

Reactive apps are all the rage lately. The Reactive Manifesto now has over 2000 signatures and all of my recent presentations about Reactive have been packed. I’ve just recorded a screencast that explains the async and non-blocking aspect of Reactive. This screencast walks through how to do Reactive Requests and Reactive Composition with the Typesafe Reactive Platform. Using Play Framework it is easy to handle async and non-blocking requests (Reactive Requests) and compose them together. This can be done with both Java and Scala but for this screencast I use Scala. Check it out and let me know what you think: