Friday, October 6, 2017

Asynchrouns and Transactional Event Listeners in Spring

The built-in event publication functionality exists from the early Spring versions and it is still useful for handling basic communication between Spring components in the same application context. In general, the application can generate application events (that can be arbitrary objects) and listen to them. The whole mechanism is really simple: using ApplicationPublisher you publish events and using EventListener you handle them. What I find especially useful is asynchronous and transactional event listeners.

Thursday, October 5, 2017

JUnit 5 - Quick Tutorial

JUnit 5 is the next generation unit testing framework for Java equipped with many interesting features including nested tests, parameterized tests, new extension API or Java 8 support to mentioned a few.

This article shows basic concepts of JUnit 5 including test lifecycle, parameter injection and assertions (basic, timeout and exception).

Tuesday, October 3, 2017

Spring Boot - spring.config.name - Case Study

Externalizing Spring Boot application properties is useful when the same application code must be used with different configuration. If the configuration is to be kept away from the source code (which is considered a best practice anyways)spring.config.location environment property can be used to point the directory location with properties files for example. On the other hand, spring.config.name can be used to change the base name of the properties file which defaults to application. The documentation reads: if you don’t like application.properties as the configuration file name you can switch to another. But in what scenario spring.config.name could be used?

Thursday, September 28, 2017

Tuesday, September 12, 2017

Lombok - you should definitely give it a try

Lombok is not a new thing in a Java ecosystem, but I must admit I always underestimated its value until I tried it or I was “convienced” to try it. I did not see much value in adding a library that generates code that can be easily generated by any modern IDE these days. So I ignored the library and I have been writing or generating tons of boilerplate code. Not anymore. In 2016 I joined a Spring-based project where project Lombok was already in place. And since then I can’t work without Lombok anymore… Why?

So what is Lombok anyways?

Shortly speaking, Lombok is a Java library that generates tons of code for the developer by plugging in into the IDE and building tools. For example, instead of adding getters, setters, equals, hashCode and toString methods to POJOs, single [@Data](https://projectlombok.org/features/Data) annotation can be used.

Build tools support, like Gradle or Maven, does not bring issues

Lombok works with Gradle with no issues. You add compileOnly dependency on Lombok and that’s basically it:

compileOnly ("org.projectlombok:lombok:${lombokVersion}")

I did not expierience any issues with Maven neither, although I mainly work with Spring related projects and recently they all are Gradle based.

IntelliJ support is good enough

I am working with IntelliJ on a daily basis and its support for Lombok works just fine. Lombok is supported by 3rd party plugin: https://github.com/mplushnikov/lombok-intellij-plugin.

The configuration of the plugin is extremely easy: you need to enable Lombok plugin and annotation processing for the project. Of course, Lombok must be in the classpath. With project configured you can start importing Lombok annotations and start using them immediately in the source code.

I did not notice issues with code completion in IntelliJ. I did not notice any delays or missing features. When I want to display code definition for the generated method it shows me the Lombok annotation - which is fine - it would nice though to see the generated code.

On the negative side, sometimes it happens that the code is not immediately available - and then manual compilation needs to be executed. This is really rare in my case.

With Lombok enabled, some features cannot be reached directly from the code editor. For example, when using @Builder annotation a lot of code is generated, including the builder class. To find usage of certain builder methods you need to do this from the Structure view..

Navigating to symbols by name in generated code is not possible but this seems not an issue: when working with Lombok you know the generated code is related to certain classes. For example, UserBuilder is related to User class so you jump into the Userto see its builder (if you really need to).

All in all, on a daily basis there are no show stoppers as it goes to IntelliJ.

Reading the code is easier

One of the main advantages of using Lombok is less code that one needs to read. This is extremely useful during the code reviews - I open the class and I immediately see if it is a anemic @Data class or maybe a @Value object, if it provides @Builderetc. And although Lombok requires even more annotation in the source code (Lombok annotations, JPA annotations, Jackson annotations, Spring annotations …) it still makes the code more concise and easier to read / review.

Lombok standarizes (some) team practices

For example, before I started using Lombok, in every project there were several approaches to create builders . With Lombok it is much easier to maintain these practices (@Builder and @Singularity) .

Lombok works fine with other libraries

I did not expierience issues with JPA or Jakson annotations mixed with Lombok annotations. I have heard, though, about issues with MapStruct and Lombok in the past but it seems to be fixed now: (https://github.com/mapstruct/mapstruct/issues/510)

Lombok annotation can be easily used with Spring components so that less code is needed while creating. For example @AllArgsConstructor can be used to inject bean’s dependencies as Spring does not require contructors to be annotated with @Autowire:

@Service
@RequiredArgsContructor
class SomeService {
    private final Dep1 dep1;
    private final Dep2 dep2;
}

Worth noting (maybe) is the fact the Spring Boot Initializer (http://start.spring.io/) provides Lombok dependency in the generated project files (one of core dependencies to be added to your new project).

Consider Lombok for your next project

Lombok is a great library that speeds up the development, makes the code more concise, easier to read and maintain. Lombok seems mature enough to give it a try. Even if you decide to use only for simple cases it can bring a lot of value to your project. Believe me or not, but I was very sceptical about Lombok until I tried it for several weeks.

Friday, June 23, 2017

Remote debugging Wildfly application in IntelliJ

Remote debugging a Java application means connecting to the remotely running application using your local development environment. Java supports remote debugging out of the box: the target application must be executed with -agentlib:jdwp[=options] option which loads Java Debug Wire Protocol (jdwp) library that allows remote debugging using for example socket connection. In this short article you will learn how to get started with debugging web application deployed to Wildfly server by using IntelliJ.

Thursday, June 8, 2017

Cleaner parameterized tests with JUnit 5

The general idea of parameterized unit tests is to run the same test method for different data.
Creating parameterized tests in JUnit 4 is far from being perfect. There are many issues with the existing architecture: parameters are defined as class fields and constructor is needed to create them, parameterized and non-parameterized tests cannot be mixed in one test class and built-in data sources are very limited. Fortunately, all of this is improved in JUnit 5!