When our Micronaut application starts we can listen for the ServiceStartedEvent event and write code that needs to run when the event is fired. We can write a bean that implements the ApplicationEventListener interface with the type ServiceStartedEvent. Or we can use the @EventListener annotation on our method with code we want to run on startup. If the execution of the code can take a while we can also add the @Async annotation to the method, so Micronaut can execute the code on a separate thread.

In our example application we have a reactive repository for a Mongo database and we want to save some data in the database when our Micronaut application starts. First we write a bean that implements the ApplicationEventListener:

As a software engineer you make architectural decisions all the time. Neal Ford calls these software engineers 'accidental architects'. I personally prefer the term implicit architects because I don’t think software engineers doing architecture is in any way an accident or even something you would not want. You’re the expert after all. Decision making is one thing though, how do you document these decisions?

Starting your next Javascript project can be frustrating or overwhelming when you have to set up your local development environment. The most of the new Javascript techniques and frameworks are dependent on node and NPM. Especially when you want to create a tutorial, blog post or prepare a workshop. The setup for each type of operating system can take to much time and your audience can lose the focus on the message you are trying to send. For this problem, CodeSandbox can help you out! On codesandbox.io you can start your next project with just one click and demonstrate, experiment or build cool stuff.

Although Java has always been awesome, Java 8 has brought the language several features the language was in dire need of. Apart from the long-awaited improved DateTime-API and the introduction of Optionals, Java 8 finally gave behaviour the attention it deserves by incorporating (a form of) functional programming into the language using lambdas.

The opportunities that Java 8 brought the language and the platform have long since been taken and functional styles of programming are part of our day-to-day routines as Java Developers. For-loops are a thing of the past for most of us, and although it had quite the learning curve, passing streams around and chaining operations on them to create some very readable code is common sense for us now.

Great projects keep moving forward. JUnit5 is available since September 2017 and Spock 1.2 is already complete. Since Spock is based on JUnit4, I wondered what it would take to use Spock 1.2 together with JUnit5.

As it turns out, it’s quite easy to make that happen. JUnit5 comes with the vintage engine to run JUnit4 based tests. If that is available on the test classpath, your Spock tests run like on JUnit4.

Making IntelliJ understand your QueryDSL generated classes needs some work. QueryDSL has an annotation processor to generate Q-classes from your entities. Just running the annotation processor doesn’t mean your IDE will understand where to find the generated classes. I was struggling to get IntelliJ IDEA picking up the generated classes. Probably there are more ways to get this done in Gradle, but I found out one that’s pretty easy to configure, without any adjustments to you IntelliJ settings. Because you could configure the annotation processor via the IntelliJ settings in the Annotation Processor screen (Build, Execution, Deployment → Compiler → Annotation Processors). It would be easier if you can achieve the same just using Gradle. With the following in your Gradle build file, it generates the classes and instructs IntelliJ where to find the classes:

If you’re using Lombok in your entities, generating the QueryDSL classes will fail, as it won’t understand the Lombok annotations. To solve this you have to add the Lombok dependency to the annotationProcessor block.

Back in '98 when I started with my CS education Java was the first programming language we were taught. Before I had experimented with QBasic, C and assembly but that was the moment where I started to really grow into being a software engineer. While I made something excursions to other languages; PHP, C#, JavaScript and even ColdFusion, Java always was my 'base' where I returned to. My great love as it were. But now she’s fallen out of fashion and I’m moving on to greener pastures: Kotlin.

Micronaut makes it possible to easily configure your application using the provided mechanisms based on Spring and Grails. This blog demonstrates how to configure a Kotlin based Micronaut application using Micronaut version 1.0.0.RC1.

Some time ago, I was working on a project where I had to fix an issue that was raised by our OWASP Zap scanner, which is a free security tool that runs in the test phase of the Jenkins build of the project. It checks for security vulnerabilities that you want to prevent from going to Production.

Jib is an open-source Java library from Google for creating Docker images for Java applications. Jib can be used as Maven or Gradle plugin in our Spring Boot project. One of the nice feature of Jib is that it adds layers with our classes, resources and dependency libraries for the Docker image. This means that when only class files have changed, the classes layer is rebuild, but the others remain the same. Therefore the creation of a Docker image with our Spring Boot application is also very fast (after the first creation). Also the Maven and Gradle plugins have sensible defaults, like using the project name and version as image name, so we don’t have to configure anything in our build tool. Although Jib provides options to configure other values for the defaults, for example to change the JVM options passed on to the application.

Let’s see Jib in action for a simple Spring Boot application. In our example we use Gradle as build tool with the following Spring Boot application: