Spicy Spring: Using @Value for Constructor Arguments

In Spring we can use the @Value annotation to set property or arguments values based on a SpEL expression. If we want to use the @Value annotation for a constructor argument we must not forget to add the @Autowired annotation on the constructor as well.

Written with Spring 4.1.6.

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Scala Snippet: multiline statements in the Scala REPL console

One of the coolest things a standard Scala install will give you, is the Scala interpreter.
Technically speaking, this is not an interpreter. In the background, each statement is quickly compiled into bytecode and executed on the jvm.
Therefore, most people refer to it as the Scala REPL: Read-Evaluate-Print-Loop.

You can access it by starting a command shell on your system and typing in ‘scala‘.
Do make sure your either run it from the place where scala is installed or have scala on your environment PATH.

By using the repl, you can quickly experiment and test out different statements. Once you press ENTER it will evaluate the statement and display the result.

Frequently you want to execute multi-line statements and luckily the repl has a solution for that.

Simply type in :paste and the repl will accept multiline statements.
To exit this mode and evaluate your code, simply type CTRL+D.

Example:

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Grails Goodness: Set Log Level for Grails Artifacts

A good thing in Grails is that in Grails artifacts like controllers and services we have a log property to add log statements in our code. If we want to have the output of these log statements we must use a special naming convention for the log names. Each logger is prefixed with grails.app followed by the Grails artifact. Valid artifact values are controllers, services, domain, filters, conf and taglib. This is followed by the actual class name. So for example we have a controller SampleController in the package mrhaki.grails then the complete logger name is grails.app.controllers.mrhaki.grails.SampleContoller.

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Bruce Lee’s Top 5 Agile Coaching Tips

bruce-lee-agile-master

When I was a kid, I was a big Bruce Lee fan. I walked around the playground rubbing my nose with my thumb. When I had a piece of rope, I had to do my version of the nunchaku routine from Way of the Dragon and made cat-like noises. Looking back at Lee, I find it quite striking how many of the principles of his fighting style Jeet Kun Do apply to agile practices.

Check out these descriptions of the fighting style:

  • “Jeet Kune Do is not fixed or patterned, and is a philosophy with guiding thoughts.”
  • “Jeet Kune Do practitioners believe in minimal movements with maximum effects and extreme speed.”
  • “The system works by using different “tools” for different situations, where the situations are divided into ranges, which is kicking, punching, trapping, and grappling, where martial artists use techniques to flow smoothly between them. “
  • “Through his studies Lee came to believe that styles had become too rigid and unrealistic. He called martial art competitions of the day “dry land swimming”. He believed that combat was spontaneous, and that a martial artist cannot predict it, only react to it, and that a good martial artist should “be like water” and move fluidly without hesitation.”

JKD is a reactive style that responds to changes in in situations and applies the best “tool” for getting the job done in the fastest way possible in that situation. JKD does not care about styles or forms for the sake of it.

Ofcourse this philosophy resonates highly with an agile mindset.

So just for fun, here are my Top 5 Bruce Lee Agile Coaching Tips

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Spicy Spring : Dynamically create your own BeanDefinition

When we a have Spring managed application, we want to let Spring manage all of our beans. Beside the regular way of creating beans with known solutions like Annotated beans, Java Configuration and XML Configuration, there is also a way in which we can create our own BeanDefinition.

With a BeanDefinitionRegistryPostProcessor it is possible to create a specific post processor which can add BeanDefinitions to the BeanDefinitionRegistry.
It differs from the BeanPostProcessor, which only has hooks for Bean Initialization (construction of your POJO), where the BeanDefinitionRegistryPostProcessor has a hook on the BeanDefinitionRegistry. This gives us the ability to define our own BeanDefinition.

First we create a BeanDefinitionRegistryPostProcessor implementation as listed in the example. We implement the required method, and will be able to add our own bean definition to the registry. The defined BeanDefinition will be picked up by the ApplicationContext and the POJO will be constructed. Our result is A Spring managed bean

Grails Goodness: Add Banner to Grails Application

Grails 3 is based on Spring Boot. This means we get a lot of the functionality of Spring Boot into our Grails applications. A Spring Boot application has by default a banner that is shown when the application starts. The default Grails application overrides Spring Boot’s behavior and disables the display of a banner. To add a banner again to our Grails application we have different options.

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Geb Gems: Running Geb Spock tests with Maven

Geb is framework which makes it easy to create functional tests for your application. Since you can use Groovy, Spock and the elegance of the JQuery selector, you can setup solid functional test very easy.

In this blogpost we will make a simple test which will test a functional part of the JDriven website. We will start our test with configuring the Maven POM file. We need to add the following dependencies.

We also need to configure the GMaven plugin which will compile our Groovy files for us and

When using Geb, a GebConfig.groovy file is requrired to be on your classpath. The best location is to put it in a recognizable location e.g. test/functional. In this file you configure your WebDriver (e.g. Firefox, Chrome etc) and the profile settings for this driver e.g. download folders, proxy settings etc.

Our test class will do a simple check to verify if there is a working link with the text ‘JDriven’ on the JDriven website which refers to the homepage.

We extend our test class from GebReportingSpec. You can also extend from GebSpec but GebReportingSpec will automatically create a screenshot if your test fails, which is more convenient

Please note that you need Firefox to be installed if you want to run the test. When you execute the following Maven command from the command line, the tests will run.

Written with Groovy 2.4.3.

Greach 2015 Conference Report

So this year I got the opportunity to speak and visit Greach 2015 in Madrid, Spain. I’ve never been in Spain before, but after visiting I definitely want to go back. Although the trip to Madrid was more cumbersome than planned, because of the strikes in France, I arrived at the speaker’s dinner on time. Just go to mention that the Madrid metro is a very pleasant way to go around in Madrid. It was good to see old and new faces and to catch up and just have fun. Friday April 10th was the first day of the conference. The conference is held at the university in the south of Madrid. Jochen Theodorou, one of the Groovy core developers, opened the day with the keynote about Groovy’s past, present and future. He gave a very nice overview of how Groovy evolved over the years and Groovy has been around already for a long time. Of course the latest news this year is Pivotal’s hands off of Groovy and Grails. Jochen explained he first gets a good vacation and then decides what to do himself. Groovy is now in the process of getting an Apache project so the continuity of the development of the language should be saved. Then the rest of the day two tracks were presented at the same time. And there were difficult choices to make. Fortunately all talks are recorded and they will be added to the Greach Youtube channel.

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Scala Snippet: Object, Companion Object and Static Methods

If you are a Java developer moving to Scala, one notable difference in terminology that can cause confusion is the term ‘object’.
In Java an object is always an instance of a class, created by calling a constructor.

Object

In Scala an object is used for defining a single instance of a class with the features you want.

In practice this means you will use it:

  • to keep utility/helper methods and constants in one place
  • to have a single immutable instance to share across a system
  • to implement the singleton design pattern to coordinate actions across a system

An object can have the same features as a class. You can extend other classes or traits. The only notable difference is that an object cannot have constructor parameters.

Companion Object

In Java there might be occassions where you want to use static methods.

In Scala you define these methods inside a ‘companion object’, which has to be defined in the same source file as the class.
The class and object can access each others private methods and variables, but you have to do it as you would call a out of scope static method in Java.

Checkout this example in the repl:

As you can see, I’ve used the “static” method from the companion object to update the shuttercount when calling the makePicture method on my canon Camera.

Finally, a singleton object that does not share the same name with a companion class is called a standalone object.

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