Conference Speaker 101

Interested to speak on conferences? But you don’t really know what to except or where to start? I invite you to read this article.

JavaOne Las Vegas 2022 Report

We even got cool T-Shirts!

OpenValue’s 11 team has visited JavaOne 2022 in Las Vegas. One talk given, over hundred of sessions attended and a couple of weeks to let it soak in later - here is what we have to share with you!

Am I Testing the Right Way?

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What can or should be considered the right size of a unit with regard to what is tested in isolation? Two unit-testing approaches explained!

What Can We Expect In OpenJDK 19?

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Although the Java 19 release is coming in September (2022-09-20), we already know what will happen in that release!

Tekton CI/CD, to build more and to maintain less

Tekton CI/CD is all about leveraging your existing Kubernetes cluster to build, test and deploy your applications and uses the same syntax as you’re used to when creating resources on Kubernetes using YAML.

Diving into JVM framework monitoring and profiling!

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Managing available resources on demand in a cloud environment can be a very challenging topic. It is worth the effort, since it may however utilize resources far more efficiently. Companies or projects are therefore very keen to migrate to the cloud providers, such as Azul, AWS, Google Cloud or others….

Thinking about massive through-put? Virtual Threads in game

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The goal of this article is to examine known facts about an upcoming Java threading model extension. No, no-worries, the current java threading model remains but behind the curtains something good is already knocking . Yes, we are talking about JEP-425: Virtual Threads…

Moving to Kotlin, powered by Engineers

About a year ago Rabobank started fully embracing Kotlin. This change happened due to the efforts of a small group of engineers who thought Kotlin is a fun but powerful language that could benefit Rabobank a great deal.

Create APIs with jwebserver from jshell to docker 

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In the age of cloud computing it is very handy to have the ability to run very simple web-server. A simple web-server that delivers static content, like JSON, read more…

Mastering command-line with factory pattern in three JVM languages

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The article investigates the code verbosity in three different JVM languages. It examines a program selection control mechanism in naive factory pattern implementation. For the example puroses the command-line is used for compiliation and programs execution…

Understanding Spring4Shell: vulnerability, attacks and mitigations

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Spring Core on JDK9+ is vulnerable to remote code execution, as described in CVE-2022-22965, also known as Spring4Shell. But what is Spring4Shell? How does it work? What types of attacks are possible and which mitigations exist? We’ll answer these questions in this article.

4+1 important features coming with Java 18 SE/JDK

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Time is running forward without any compromises and the six month JDKrelease period is over. Similar to people expecting spring and nice weather, the Java community is excited about the next SE and JDK release that holds number 18. Yes, Java 18 is here and in this article we explore the most important changes together with features added since the preview.

Plugin and Play

How to verify your Kotlin project in a Kotlin way? Simone is talking about test coverage and about style linter. Wouldn’t it be great if we can really use Kotlin in the full spectrum and use tools that support those features?

Observability 4 JVM Frameworks with Grafana in Java and Kotlin

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In the time of cloud and distributed applications it is becoming more and more important to be able to evaluate a functionality at runtime, an aspect which is referred to as observability. A cloud based application is usually set up as the collection of different subsystems that may be located in one or more network zones or machines. These subsystems communicate between each other by passing messages (signals) and executing desired actions to each other. The whole collection then appears to the end user as a single coherent system.

Building a career as a speaker

How do you build a career as a speaker? What are the ingredients for a great talk? Why is sharing knowledge important? Watch this interview with our CTO Bert Jan Schrijver and learn how to kickstart your speaking career.

Understanding Log4Shell: vulnerability, attacks and mitigations

Log4Shell (CVE-2021-44228) is a zero-day vulnerability in Log4j, a popular Java logging framework. But what is the Log4Shell vulnerability? How does it work? What types of attacks are possible and which mitigations exist? Watch this video for answers!

Java Flight Recorder: Knocking on the Java & Kotlin apps profiling doors

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Nowadays the IT world often spells terms like SRE or latencies, but how to measure this in an accurate way without relying on ‘random’ samples. The goal of this article is to examine the possibilities of profiling a Kotlin and a similar Java application with Java Flight Recorder to get a better understanding of their behavior compared to each other.

Software architecture in a DevOps world

Most modern software teams strive for Continuous Delivery of business impact with a DevOps mindset: you build it, you run it. With short iterations and continuous feedback loops, teams deploy new software to production daily. But how about the role of a software architect in such a fast-paced world? With daily deployments, is there even time for software architecture?

Why is testing so difficult?

There are hundreds, if not thousands of blogs, papers, videos and talks that describe how and what to test and especially why! In my talk I want to shed light on possible reasons for test fatigue and show possible solutions on how test coverage can be increased in large enterprise projects and how developers can enjoy testing more!

Debugging distributed systems

Debugging distributed systems is not easy. When two components don’t play nice together, the cause could be virtually anything: software, DNS, routing, firewalls, proxies, load balancers, TLS.. and more! In this talk, I’ll share my experience with debugging distributed systems. We’ll look at typical issues and I’ll introduce a structured ways to debug those issues and find their root causes.

From Spring Boot to Quarkus

When you’re building (micro)services, you have lots of framework options. Spring Boot is no doubt a popular choice. But there’s more! Take Quarkus, a framework that’s considered the rising star for Kubernetes-native Java. It always depends what’s best for your situation, but how to choose the best solution if you’re comparing 2 frameworks?

Embrace the Kotlin ecosystem at the back-end side

Kotlins ecosystem for server-side development is growing very fast. While Spring is also hopping on the Kotlin train, the rest of Kotlins ecosystem is growing fast. More and more new frameworks are popping up implementing different point of views on how to build your service. Those new frameworks might change our ways of developing back-end applications. Lets have a look out there!

Testing of email notifications with GreenMail

Sending emails or receiving and processing emails is something that a lot of applications feature to their users. But how do you know that the code doing this actually works? GreenMail is an open source, intuitive and easy-to-use suite of mock email servers for testing purposes. In this presentation you will learn how to leverage GreenMail to manually and integration test your email functionality.

Introduction to remote debugging of Java applications

In this talk, I will show you how you can connect your remote Java application with your local IDE to start debugging. You’ll learn how to use SSH to connect to a secured environment for debugging and profiling the Java application. And I’ll also show you some easy tricks, you can use for your future analyzing sessions. After this talk, you’ll be ready to start remote debugging Java applications yourself!

What makes a good developer?

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In the past 20 years I’ve been able to work with many developers. Together we’ve worked on very large to the tiniest of projects, from huge corporate applications to simple web forms that deliver enormous business value. From beautiful new ‘greenfield’ applications to software written long before I was born.

Building a platform native CLI in Kotlin with Clikt and GraalVM

Most developers love working with command-line interfaces (CLI’s) to speed up and automate tasks. But how about building a beautiful and feature rich CLI in a JVM language? Sounds impractical, since JVM languages need a virtual machine to run on. Well, not anymore! With Clikt and GraalVM, it is possible to create these CLIs with ease, and even create native platform binaries for every major platform architecture.

Mutants to the rescue: How effective are your unit tests?

We write tests to tackle bugs, verify functionality and to ease maintenance. Using code coverage as our metric we might deem ourselves safe and our tests flawless. But how can we be sure that our tests are okay? In this talk we will enter the world of mutation testing. We will cover mutation tools, how they work, how to get started and how to integrate it in your builds.

What do you know about Java compiler optimizations?

The Java HotSpot compilers support a suite of advanced optimizations to enable high performance programs. Some of these optimizations include method inlining, removing unnecessary checks and loop unrolling. The compiler does this at different times, but what do you already know about these optimizations? In this talk, Ill test your knowledge of different optimizations via an interactive quiz.

End-2-End test environments, a dead End road

With the rise of Distributed Architecture, independent DevOps teams and automated CI/CD the End-to-End test environments needs to be reconsidered. They become flaky, shaky, untrustworthy and hard to maintain. Why are End-to-End test environments a dead End road and what are the alternatives.

The Magic of Music Matching

The first time I used Shazam (the music matching app) it felt just like that: pure magic. The app shortly listens with the microphone and tells you which song is playing. After a weekend of studying, reading scientific papers and experimenting and coding: I had a working Shazam clone written in Java. During this talk I’ll reveal what I’ve learned and what algorithms and tricks being used.

Going full stack with GraphQL

REST is a great convention on paper, but is it actually good enough for today’s variety of clients like web, mobile, IoT etc? Is there a better alternative? GraphQL’s query language can drastically change the way you think about data models and state-management. In this talk we’ll learn how to put GraphQL (Java) in front of an existing Java REST backend and how to introduce compile time coupling between clients and server.

Concurrency in Kotlin: how coroutines make it easier

Concurrent software is hard to get right, as we’ve seen in the previous article, “When flows split”. Concurrency is even harder to express. Most concurrent code is being written in a way that makes our heads spin every time we need to read it. Let us see how Kotlin helps us write concurrent code that is clearer and more efficient from the start.

A guided tour through automated testing with Cypress.io

Cypress is a complete end-to-end testing experience for anything that runs in a browser. Cypress promises to be more developer friendly than Selenium; let’s see if that’s true. In this session we’ll show how we’ve used Cypress to make feature development easier at a Dutch education company, write end-to-end tests at a Kenyan healthcare company, and test individual components at bol.com.

Spring Boot: From Java Web MVC to Kotlin WebFlux

Spring Boot has been around for some time and still seems to be the most popular framework when it comes to building modern web applications. Similarly about Kotlin language. It’s not as old as Spring framework but it’s been highly accepted and used by many developers. In this post, we’ll look at moving from Java Web MVC to Kotlin WebFlux.

Building serverless Java applications using Micronaut and OpenFaaS

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When working on microservices in the Java ecosystem, especially using Spring (Boot), you will notice the long start-up time that applications will have, let alone the high memory consumption they will have. Looking at a framework such as Micronaut could help out to reduce this overhead without loosing any developer’s productivity. Let’s dive into it!

Why we gave 50+ tech talks at 19 conferences

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We started OpenValue almost 2 years ago. One of the key values of our company is sharing knowledge. Next to fun and craftsmanship. This all comes together with our activities in the international Java community. I’ll explain why.