Java Bean Validation is an Anti-Pattern

Avoid Inconsistent Builder With Lomboks @Builder

In a project I worked on I saw that nearly every entity and value object was created with Lomboks @Builder . Their reason is that it makes it easier to construct these objects - especially for tests. But it comes with a cost. The problems that these builders create can’t be detected by the compiler and are especially dangerous in every CI environment.

Let’s look at an example. This is our object that uses the builder for construction:

Marcus Held

Best Practices For Unit Tests

Unit tests had a bad reputation in many teams I worked with. To my confusion I even experienced that a team wrote a hell lot of integration tests but rarely any unit tests. This is contrary to the well-known testing triangle, and surprised me quite a bit. The reason - as I was told - was the experience of the team. “When you change something you have to adapt many unit tests”, was the common tenor. So they decided to write integration tests which call the real endpoints instead. This comes with a cost. Generally you have a harder time to identify where a issue lies when an integration test - which goes through the whole system - fails. Also the runtime will not lead to fast feedback - one of the main benefits of having proper unit tests. I discovered that the issue is that many developers never learned how to write proper unit tests. In this post I will cover the best practices that I developed throughout my career.

Marcus Held

Boost Your Development With Proper API Design

In this post we’ll go through an example application and see which methods and principles we can apply to build a robust application that is easy to maintain, extend, understand and use. In general, this is a subject with a much larger scope than a simple blog post can provide, so the content is neither complete nor exhaustive, but a selection of topics that I visited recently. We use an arbitrary business case where we can buy and sell resources on a market. Our example is implemented with Java using Spring Shell for a simple frontend representation. However, please keep in mind, even if technology you use operates differently, the principles stated in this post remain true for every language. Without further hesitation let’s start with an example of how our application works:

Marcus Held

Never Design A Class That Knows How It's Used

When you design a class you should never design it in a way that the class itself knows how it is used from the outside. Breaking this principle will make it difficult for other developers providing other implementations. I recently stumbled upon an implementation of different entities where the implementation had to provide a unique id for itself. Why this is causing problems and how you better design such a situation I’ll explain in this post.

Marcus Held

Distinguish Between Optional and Mandatory Parameters in the Builder Pattern

After reading through Designing Bulletproof Code by Otavio Santana I stumbled upon its example of using a builder pattern. While this was not the focus of the article itself I also realized that I saw the issue in the past a lot and I ran in it as well. The widely spread understanding of the builder pattern (as described in Effective Java by Joshua Bloch) does not differentiate between optional and mandatory parameters and that makes their usage not easier but harder.

Marcus Held