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Author Archives: Michael Scharhag

Michael Scharhag
Michael Scharhag is a Java Developer, Blogger and technology enthusiast. Particularly interested in Java related technologies including Java EE, Spring, Groovy and Grails.

Injecting domain objects instead of infrastructure components


Dependency Injection is a widely used software design pattern in Java (and many other programming languages) that is used to achieve Inversion of Control. It promotes reusability, testability, maintainability and helps building loosely coupled components. Dependency Injection is the de facto standard to wire Java objects together, these days. Various Java Frameworks like Spring or Guice can help implementing Dependency ...

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Understanding JUnit’s Runner architecture


Some weeks ago I started creating a small JUnit Runner (Oleaster) that allows you to use the Jasmine way of writing unit tests in JUnit. I learned that creating custom JUnit Runners is actually quite simple. In this post I want to show you how JUnit Runners work internally and how you can use custom Runners to modify the test ...

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Using IntelliJ bookmarks


This is a quick post about IntelliJ’s nice bookmark feature. IntelliJ gives you the option to bookmark single lines of code. After a line has been bookmarked, you can use various ways to jump directly back to this line. So it can be a good idea to bookmarks code locations you often work with. To create a new bookmark you ...

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Using Markdown syntax in Javadoc comments


In this post we will see how we can write Javadoc comments using Markdown instead of the typical Javadoc syntax. So what is Markdown? Markdown is a plain text formatting syntax designed so that it optionally can be converted to HTML using a tool by the same name. Markdown is popularly used to format readme files, for writing messages in ...

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Building a simple RESTful API with Spark


Disclaimer: This post is about the Java micro web framework named Spark and not about the data processing engine Apache Spark. In this blog post we will see how Spark can be used to build a simple web service. As mentioned in the disclaimer, Spark is a micro web framework for Java inspired by the Ruby framework Sinatra. Spark aims ...

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Java File I/O Basics


Java 7 introduced the java.nio.file package to provide comprehensive support for file I/O. Besides a lot of other functionality this package includes the Files class (if you already use this class you can stop reading here). Files contains a lot of static methods that can be used to accomplish common tasks when working with files. Unfortunately it looks to me ...

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Groovy 2.3 introduces traits


A few days ago the second beta of Groovy 2.3 got released. One of the major new Groovy 2.3 features are traits. A trait is a reusable set of methods and fields that can be added to one or more classes. A class can be composed out of multiple traits without using multiple inheritance (and therefore avoiding the diamond problem). ...

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The Grails depedency injection inheritance pitfall


This blog post is about a small pitfall you should be aware of when combining dependency injection in Grails with inheritance. I think the problem is best explained with a piece of example code. So let’s look at the following two definitions of Grails controllers.             class FooController {   TestService testService   def foo() {     // do something with testService   } } class BarController extends FooController {   TestService testService   def bar() { ...

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