Tech

Sometimes when writing an application we might consider using an in-memory file system to speed up data access or to create some kind of cache. There are different libraries to help us here but one looks especially promising for me because it supports almost every functionality of the Java NIO File APIs added in Java 7 – from creating, reading, deleting files and directory to handling symbolic and hard links or watching directory changes with a WatchService. ...

For the most of us developers, generating Java source files is an occasionally happening task and we’re dealing with it e.g. when writing annotation processors, writing tools or interacting with meta-data files. JavaPoet is a nice library to simplify such tasks, offering an intuitive fluent-builder API to generate source files in no time. In the following tutorial I’d like to share a few examples by writing code generators with the help of this library. ...

When it comes to indexing in a Neo4j graph database, different options exist for a developer to create and maintain the index. In the following short examples I’d like to demonstrate different possibilities for index management. Figure 1. Simple Domain Model Dependencies Only one dependency is needed to run the following examples and start an embedded neo4j server – I’m using Gradle here to manage my dependencies but Maven, Ivy, SBT should work without a problem, too. ...

When there is the need to create load tests or performance tests for an application, Apache JMeter is a handy tool and set up with ease. In the following short tutorial I’d like to demonstrate how to configure JMeter to log into a Java EE web application with multiple users specified in a CSV file, how to generate some basic reports and how to integrate JMeter into a mavenized build using the JMeter Maven Plugin. ...

Having written about the basics of using Cucumber in a Java project in my last blog article, I now would like to demonstrate how to use a similar setup in a Java EE web project with Arquillian and the Cukespace library. In the following tutorial, we’re going to write a full Java EE web application and add BDD-style tests to the project so that we’re able to test our business layer on the one hand and the user interface on the other hand using Arquillian Drone and Selenium. ...

Whether behaviour-driven-development, specification by example or acceptance test driven development is the goal, the Cucumber framework eases our life when we need to establish a link between the non-technical, textual description for a new feature and the tests that prove that the application fulfils these requirements. In the following short tutorial I’d like to demonstrate how to add Cucumber to a Java project and how to write feature descriptions and test-cases for each step of these descriptions. ...

Especially when it comes to testing, setting up a decent environment for a secured Java EE web application isn’t always an easy thing to do. In the following tutorial I’d like to demonstrate how to create a secured web application using form-based authentication and a JDBC realm to fetch users and roles and how to run the application in an embedded container for testing and development. Additionally I’d like to show how to write and run integration tests to verify the security setup using a setup of Maven, Embedded GlassFish, Arquillian, jUnit and rest-assured. ...

Having written two articles about different websocket based chat server implementations in Java, I was recently asked how an implementation of the client side would look like in Java. That’s why I added this article to demonstrate how to create a websocket chat client applications within a few steps with the Java API for Websocket. In the following tutorial, we’re going to write a text-based chat client for the console first and afterwards we’re going to program a chat client with a graphical user interface, implemented in JavaFX. ...

Apache Camel not only is one of my favourite frameworks ever but it also allows the humble developer to create a full blown chat bot within a few lines of code and using the Camel XMPP component. In the following tutorial, we’re going to create a simple chat bot and since Atlassian’s HipChat basic plan is now free for unlimited users, we’re using HipChat as our play- and testing ground for the bot. ...

Recently I needed to modify some excel files and to add some aggregated formula fields to a sheet and the following snippet did the work for me. Figure 1. Modified Excel File with Formulas Dependencies Just two dependencies needed here: One for Apache POI and one for the Office Open XML Documents API. <dependency> <groupId>org.apache.poi</groupId> <artifactId>poi</artifactId> <version>3.10.1</version> </dependency> <dependency> <groupId>org.apache.poi</groupId> <artifactId>poi-ooxml</artifactId> <version>3.10.1</version> </dependency> Sample Excel File Our sample excel file is quite empty just some empty customer information and a chart that is bound to the data grid. ...