Home » Author Archives: Arthur Arts

Author Archives: Arthur Arts

Arthur Arts is an experienced Enterprise Java software engineer and hands-on Agile Coach and Scrum Master. He has a strong focus on agile engineering principles and practices and loves to share his knowledge and learn from others. He has his own company Coded Value, is a passionate photographer and writes for agilearts.nl.

Code Challenge “Vrolijke Framboos” Postmortem

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Tuesday we had our second ever “Vrolijke Framboos” (Dutch for Happy Raspberry) Java code challenge at JDriven and it was a blast! This year’s challenge was to create a REST service client that would play a number guessing game with the server. After setting up a session you would guess a number and the server would respond with either “lower”, ...

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Scala Snippet: How to filter a list in Scala

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In Scala, filtering and processing collections is easy and elegant. There are many filtermethods available, but the most used will probably the basic filter method. Here’s a code example of some filtering on my (ex)camera collection. The filter method will not only work on Lists, but on any Scala collection. object MyCameraCollection02 { class Camera(_brand: String, _model: String, _sensorType: String, ...

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Bruce Lee’s Top 5 Agile Coaching Tips

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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 ...

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Scala Snippet: Object, Companion Object and Static Methods

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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 ...

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Scala Snippet: Case Class vs plain ordinary Class

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In Scala there exist the construct of a ‘case class’. According to Martin Odersky this supports you to write a “regular, non-encapsulated data structure”. It always seems to be associated with pattern matching. So when to use a case class and when to use a ‘plain’ class? I found this nice explanation stating: “Case classes can be seen as plain ...

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Alternating between Spray-servlet and Spray-can

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On a server you may want to deploy your application as a war. How to build a war with spray-servlet. Locally it’s easiest to run without an application server. We include both the spray-servlet and spray-can dependencies: name := "sprayApiExample" version := "1.0" scalaVersion := "2.11.6" libraryDependencies ++= { val akkaV = "2.3.9" val sprayV = "1.3.3" Seq( "io.spray" %% ...

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Building a war with spray-servlet

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We will use spray-servlet to build a war file of our API. So we can run it in a java app server. I assume we already have a working REST API. We will need a web.xml, under src/main/webapp/WEB-INF/: <?xml version="1.0"?> <web-app> <listener> <listener-class>spray.servlet.Initializer</listener-class> </listener> <servlet> <servlet-name>SprayConnectorServlet</servlet-name> <servlet-class>spray.servlet.Servlet30ConnectorServlet</servlet-class> <async-supported>true</async-supported> </servlet> <servlet-mapping> <servlet-name>SprayConnectorServlet</servlet-name> <url-pattern>/*</url-pattern> </servlet-mapping> </web-app> We need an sbt plugin to ...

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Building a rest api with spray

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Building a rest api with akka and spray is easy. This is how I did it: SprayApiApp:                   import akka.actor.{ActorSystem, Props} import akka.io.IO import akka.pattern.ask import akka.util.Timeout import spray.can.Http import scala.concurrent.duration._ object SprayApiApp extends App { //we need an ActorSystem to host our application in implicit val system = ActorSystem("SprayApiApp") //create apiActor ...

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Chaining futures in scala

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Suppose I want to make coffee. This involves 4 steps: 1a. grind coffee beans 1b. heat water 2. combine 3. filter All these steps take time, so they return a Future. This is our domain:     import scala.concurrent.{Await, Future} import scala.concurrent.ExecutionContext.Implicits.global //We need an executionContext to run futures import scala.concurrent.duration._ //This provides the "1 second" syntax class CoffeeBeans() class ...

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Introduction to Spring profiles

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So many men, so many minds. When we are implementing software for different customers we sometimes need to handle various requirements for the same project. For example Customer A needs SAML authentication and customer B needs LDAP authentication. With Spring Profiles (available from Spring 3.1) we are able to provide a way to segregate parts of our implemented application configuration. ...

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