Novice to Coin Part 1 - Blockchain Data Structure

Every day new developers are learning just how simple blockchain technologies are. One of the first things you may notice is that the collection of algorithms are profoundly clever, but the mechanics of creating a verifiably immutable chain of data is borderline trivial. If you need proof, take a look at how many introductory blogpostsarebuildingatoyblockchain. These all include working implementations of a blockchain. One good reason to implement your own is to prove to yourself just how trivial the data structure is. Certainly, my first reaction to reading up on bitcoins block header was: is this all?

Of course, the answer is no. Creating a blockchain is table-stakes, and from there a series of clever algorithms allow transactions to occur without a central authority. But this structure is the heart of all that follows, so building a blockchain is a great place to start.

Like you may have guessed, a blockchain contains a series of blocks. The smallest useful block contains an arbitr…

Novice to Coin Introduction

In this series of blog posts, the concepts needed to understand and implement the fundamentals of blockchain and cryptocurrency technologies will be introduced. During each post a new cryptocurrency concept will be introduced, then the technical details will be implemented as a practical demonstration of how they work. The currency will be implemented with Kotlin, which I've found to be expressive while maintaining readability. Future iterations of this project may include alternate implementations in other languages.
This series will be broken into several parts: Data StructureCurrency and TransactionsDecentralization and MiningOptimization: Merkle TreesData Structure An introduction to the mechanisms that allow us to verify that data in the chain has not been tampered with. We'll begin with a high-level explanation of how it works and move onto a succinct implementation which will serve as a stepping stone for the following posts.
Currency and Transactions Once familiar with …

Building a REST Client with Kotlin and Retrofit2

If you regularly work with REST endpoints you're probably used to a lot of tedium. Between carefully constructing the parameters, encoding data in just the right format, efficiently sending the requests, parsing the results and handling errors at every step along the way; there is a lot of room to make mistakes.
For simple APIs, it often makes sense to manually format the request and send it out. Checking a status code, and maybe mapping results to an object aren't that big a deal for a simple API. But what if there are 20 different endpoints? Or you need to manage authorization headers? Eventually, it makes sense to start looking for a wrapper library, or maybe making your own wrapper layer.
That's what this post is about.

For JVM developers, pairing Kotlin, Retrofit2 and Gson make it easy to bang out a type-safe client wrapper.

Let us jump right into the code:

// Create data classes for serializing inputs and outputs. data classResults<out T>( val next: String?…

Netbeans Platform: Mac OSX App Bundle and Embedded JRE with Maven

One problem every Java Desktop developer has to deal with is that Java apps just don't act like native applications. Whether it's the JRE dependency, the swing look and feel, or just bad memories about slow performance in old versions of Java. On Mac OSX there is an additional hurdle where users expect their applications to be a .app bundle inside a DMG image with a shortcut to /Application allowing them to drag/drop the installation. The built in Netbeans Platform installer is nice, but it's a far cry from the native behavior.

With that in mind, I'm going to describe how you can really step up your Netbeans Platform Maven build to include an OSX deployment with a bundled JRE all packaged up as an APP inside a DMG image. What a mouth full.

All of the source code for my implementation in Universal Gcode Sender can be found on GitHub in this commit. The techniques used in this post were heavily inspired (and in many cases copy/pasted from) the Gephi project, which has a …

Netbeans Platform: Good, Bad and Ugly

The Good
The Netbeans Platform is incredibly simple to get started with. There are extensive tutorial based guides to get you started, like this tutorial about creating a CRUD application with zero code, or making a paint app, and videos too, not to mention Geertjan's Blog which goes into many advanced examples. If you're using the Netbeans IDE you also get a huge assortment of wizards to help you along with various annotation-based integrations. The wizards have excellent ANT support and pretty good Maven support as well. There are many advanced features in the box from window management, plugins, configurable key-bindings and an auto-update framework.

The Bad When you want to do something advanced which isn't covered by a tutorial, you quickly need to roll up your sleeves and dig into the source code. For example, if you choose to migrate from the default ANT build to Maven, this guide is lacking if you aren't very familiar with Maven. Or even if you used the built …

UGS 2.0 to Netbeans Platform first impressions

For the past year Universal G-code Sender has suffered pretty severe feature creep. Lots of people had lots of good ideas, but it made the front end code confusing and hard to extend. In large part this is just because it's hard to compartmentalize a complex GUI. GRBL has had a lot of interesting features added in the past year which are begging to be leveraged, but UGS wasn't in a position to use them. With all this in mind I started trying to come up with a solution.

The first step was to decouple the "model" object from the GUI. Inspiration for this started nearly a year ago when Bob Jones implemented a web interface for UGS. Bob made a thin API layer which exposed a few simple functions and allowed him to build a completely separate web-based user interface. This pattern is known as Model-View-Presenter, and allows for multiple front ends which use the same back end code. It enhances test-ability of the business logic and helps facilitate a flexible front end. It…

Automated builds with Netbeans Platform 8.0.2

I've been converting UGS to run on the Netbeans Platform over the past week, and in general its been great.  The features and documentation I used while migrating UGS away from Swing were very well done. So aside from a couple hiccups, the Netbeans Platform has been great. Until a few days ago when I decided it was time to integrate my new changes with my Jenkins CI server.

It turns out that you can't build a Netbeans Platform application without connecting to the Netbeans IDE first. This has to do with the extra modules, platform components and build harness. Searching the subject online provides a lot of documentation, everything I've found is either out dated, contradictory, or I could only get it working with a new project and not my existing one.

The final solution was so simple, and minimally invasive that I wanted to create this blog post.

There are 4 interesting files for a Netbeans Platform build:
build.xml - Some documentation suggests adding a download-netbeans-r…