I was recently asked to convert a Spring Boot-based "CLI" to a real CLI utility. It was actually just a normal Spring Boot application with REST endpoints that we'd hit with curl. Pretty ugly. After a few frustrating hours, I finally settled on a solution that seems to work pretty well for us. It uses Spring Boot, of course, as that's our library of choice, plus JCommander for the argument handling. This is a pared-down example of how the application is structured. And because I care about of each you deeply, I'll present it in Java AND Kotlin. :)

For those of you in a hurry, you can get the complete code in my GitHub repo . Everyone else, feel free to read along.

Recently, I started working on a new project and I wanted to give Jooq a go. I also wanted to integrate Flyway : I wanted jOOQ to generate its various classes based off the database schema, and I want to Flyway to create that schema. That's all easy enough, but I'm resisting, right now, committing the generated classes to source control (to avoid the churn and additional maintenance), so how do I make that happen with as little work as possible? How do I make it work in a CI environment? Thanks to Maven, the answer is lots and lots of XML. :) Let's take a look...

Over the years, I've found myself processing a set of data and storing it in a Map, say, something like Map<Long, List<String>> (think something like a list of Room objects, keyed by a building id). I have found myself writing it something like this (in non-idiomatic Kotlin):

Fortunately, the Kotlin standard library has a better way:

If key is not found, the lambda is run, adding the result to Map and return to use the value, new or otherwise, to which we add bar. Much more concise. :) Generally speaking, any time you can let the language/compiler do the work for you, you're going to be better off.

One of the great things about Spring Data Repositories is that they provide a number of query methods out of the box, with the ability to add additional queries simply by adding carefully named methods to the interface, and Spring generates the actual implementation for you. Sometimes, though, you do need to color outside the lines a bit. Thankfully, Spring allows us to do this. You just have to ask it nicely. Here's now.

Thanks to haste and some sloppy copy-and-paste, today I deleted the wrong remote Git branch. There's nothing like learning in a panic, but that's what happened. Here's what I learned on how to fix that.