StackHolder - Jakub Kubrynski

There are many ways of dividing whole application into packages. Discussions about pros and cons of packaging by feature or by layer can we found on many programming blogs and forums. I want to discuss this topic starting from testability and see if it will drive to any meaningful result. At the beginning let's try to describe what we usually want to test in our applications across different layers. Let's assume standard three tier architecture. At the bottom we have data layer. Depending on our attitude to Domain-Driven-Design we'll try to maximize (for rich, business-oriented entities) or minimize (for anemic entities built only from getters and setters) test coverage. In the second approach it's even hard to say about any tests, unless you don't trust Java and want to verify if get can retrieve value assigned before by set invocation. For rich entities we definitely want to verify business logic correctness. But to be honest it almost always can be done by si...

Few years ago in Java world it was almost obvious that every "enterprise" class project needed JPA to communicate with database. JPA is a perfect example of " leaky abstraction " described by Joel Spolsky. Great and easy at the beginning but hard to tune and limiting at the end. Hacking and working directly with caches, flushes and native queries is a daily routine for many backend developers involved in data access layer. There are enough problems and workarounds to write a dedicated book "JPA for hackers", but in this article I'll focus only on concurrent entity processing. Let's assume the situation: we have Person entity which in some business process is updated by some service. @Entity public class Person { @Id @GeneratedValue private Long id; private String uuid = UUID.randomUUID().toString(); private String firstName; private String lastName; // getters and setters } To ignore any domain complexity w...

Advantages coming from dependency injection can be addicting. It's a lot easier to configure application structure using injections than doing all resolutions manually. It's hard to resign from it when we have some non-managed classes that are instantiated outside of the container - for example being part of other frameworks like Vaadin UI components or JPA entities. The latter are especially important when we're using Domain Driven Design . During DDD training ran by Slawek Sobotka  we were talking about options to remove "bad coupling" from aggregate factories. I'm sure you'll admit, that it's better to have generic mechanism able to "energize" objects by dependencies defined by e.g. @Inject annotation than inject all necessary dependencies into particular factory and then pass them into object by constructor, builder or simple setters. Spring framework brings us two different solutions to achieve such requirement. I'll now describe ...