Blog about Spring, Kotlin, Java, JVM, Clean Code, Continuous Integration and many more topics from my daily work

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The implications of JPA always manage to surprise me. Yesterday a colleague of mine made me aware of a warning in IntelliJ. The conversation went like that: “Marcus, in your blog you explained that we should check constraints in the constructor instead of bean validation”. Me: “yeah”. “I wanted to make it right, but when I do it in this entity IntelliJ warns me with Accessing non-final property name in constructor”. So I dug into it. Fearing my conclusion would change the recommendation that I gave in (k)lean JPA two years ago.

From time to time I experience that an application is unnecessarily configurable. In a recent project I experienced how too many options lead me to feel much more complexity and increased my mental load. Looking deeper into some of the values I saw that these were actually constants that would be dangerous to change “on-the-fly” anyway. In this post I reflect on this and share my thoughts.

Over the past years I attended hundreds of interviews. Many candidates proudly told tales on how they develop their projects with a microservice architecture. Often (I don’t want to say “always”, but from my memory I think it actually is “always”) it does not require many questions to see that they used a rocket launcher to kill a mouse. Microservices are hard. Everyone who experienced the pain of operating such an architecture can relate to it. The complexity kills you at one point or the other. You already had to do multiple refactorings of your architecture - because your domains didn’t work out. I wonder - why is this architecture so appealing to developers? And then I remember why I found them appealing 10 years ago.

The javax.validation package is widely used in our industry. And I don’t like it. I believe using bean validation is an anti-pattern. It hides business relevant constraints, it leaves the choice when a validation happens to other framework code, and I even saw cases where developers expected that the validation “just had to take place”, but it never happened. Of course, there was also no test for it. And speaking about tests - testing these business relevant constraints is painful as well.

Today I write an unusual post for this blog - A personal note. I recently took the responsibility of the System & Infrastructure department. As you can imagine taking over such a position comes along with a lot of work - especially when you didn’t get rid of the old responsibilities yet. That’s the main reason why I didn’t write a blog in the past months.

In my last post I reflected the downsides of using numerical types for the primary key of an entity. We should avoid these issues all together by using UUID instead and in this post I will discuss the up- and downsides of this approach.

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About Me

Picture of Marcus Held

Marcus Held

IT Backend Consultant

It is my passion to support difficult backend projects. With more than 15 years of experience in software development and the last 12 focused on the JVM with Spring, I help companies to identify the critical points in their project and correct them in a sustainable way.

Prior to my freelance work I managed the backend department at grandcentrix with more than 30 employees. There I was involved in developments like Modbus Cloud Connect or in projects of customers like Brose, Bucher, Gardena, Hörmann, Miele or Migros. As a software developer I was responsible for the development of several online games like Rise of Cultures, Sunrise Village, Goodgame Empire or Legends of Honor with up to 220 million registered users.

At the age of 12, I had my first experience with programming. At 15 I started working professionally for companies and by 18, prior to finishing school, I founded my first company: Web as Art.

  • (k)lean JPA — Fallstricke und Clean Code mit JPA & Kotlin KKON digital 2021

    150 Kotlin enthusiasts throughout Germany attended the KKON 2021. In my talk I described pitfalls with JPA and how you avoid them in kotlin.

  • Boost Your Development With Proper API Design code.talks 2019

    With 1600 attendees is code.talks the largest developer conference in Germany. Around 400 people listened to my talk where I discussed several aspect of robust software architecture design.

Rise of Cultures
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What is it?

Rise of Cultures is a simulation game where you guide your civilization through the ages, meet other cultures, conquer continents and built up your cities.

What did I do?

I developed and maintained the backend, which we developed with Java, Spring and Hibernate. When I worked on the project we released it for the first time on the US market to test early retention KPIs.

Sunrise Village
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What is it?

Sunrise Village was a character driven simulation game in which the player built up a village and explored the world with his character. The game featured a rich exploration of the world and an extensive production simulation.

What did I do?

I developed and designed the server from the early days of production with Java, C#, Spring, Hibernate, RabbitMQ and .NET Core. One of the main features of the backend was a .NET Core application that used the same business logic as our client. The backend was capable to simulate multiple players moving on the same map.

Gates of Epica
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What is it?

Gates of Epica was an action RPG developed with the Unreal Engine 4 for iOS and Android. In the game the player fought for loot and glory in more then 600 hand-crafted missions and joined glorious multiplayer boss fights where many players fought a boss for days.

What did I do?

My responsibility was the development of the backend and game logic. We used Java with Spring Boot, postgreSQL and hibernate.

Legends of Honor
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What is it?

Legends of Honor is a massive multiplayer online strategy browser game. In the game you take control over a medieval kingdom and move through the world with your army in real time.

What did I do?

When the project was started I joined it right away as the first backend developer. In this role I had the technical responsibility to design the server architecture and lead a team of 10 backend developers until the launch of the project.

Shadow Kings
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What is it?

As a successor of Goodgame Empire it was planned to target a more casual audience with a similar gameplay. Shadow Kings got released on PC, iOS and Android.

What did I do?

I took over the project in the last months of its existence as the first backend developer. In this time it was my responsibility to lead a team of 6 backend developers and to fork off the server from its origins in Goodgame Empire.

Goodgame Empire
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What is it?

Goodgame Empire is a massive multiplayer browsergame with more than 70 million registered players. As a player you build up your castle to rule over four different kingdoms.

What did I do?

I started working on Empire 2014 and was one of the main backend developers of one of the two feature teams we operated. In this project we operated a Java based server which handled thousands of concurrent users with a high amount of requests per minute.