Archive for the ‘Java’ Category

Creating a XMPP Chat Bot with Apache Camel

Sunday, October 12th, 2014

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.

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Snippet: Modifying Excel Files, Adding Formulas with Apache POI

Monday, September 29th, 2014

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.

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JAX-RS Server API Snippets

Sunday, September 28th, 2014

Because a lot of my current projects are using JAX-RS in different versions I’d like to write down and share some frequently used snippets for implementing RESTful web-services with the JAX-RS specification here.

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Java EE 7 JMX Reports with Yammer Metrics

Tuesday, August 26th, 2014

There are several ways to aggregate and report application performance indicators in a Java application. One common way here is to use Java Management Extensions (JMX) and MBeans.

The Yammer Metrics Library eases this task for us and simplifies the aggregation of different reports.

In the following tutorial, we’re going to set up a full Java EE 7 web application by the help of Maven archetypes and we’re running the application on WildFly application server that is downloaded and configured completely by the WildFly Maven Plugin.

Finally our application is going to use the Java API for JSON Processing to parse lists of public repositories from the Bitbucket REST API to aggregate different reports, exported via JMX so that we’re finally able to view these reports with jconsole or jmeter.

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Java EE 7 Database Migrations with Liquibase and WildFly

Thursday, July 31st, 2014

I have written about other database migration frameworks before but in this article I’d like to cover the Liquibase framework in combination with WildFly as Java EE 7 compatible application server.

In the following tutorial, we’re going to write a full Java EE 7 book store application with a few steps and with Liquibase on board to create the database structure and insert example data into the database.

Thanks to the WildFly Maven Plug-in we even do not need to download and configure the application server but let Maven and the plug-in do the work for us.

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XMLBeam: Snippets and Examples

Tuesday, July 22nd, 2014

XMLBeam is an interesting library using an approach of projecting parts of an XML DOM tree into Java using some simple interfaces, annotations and XPath expressions.

In the following article, I’d like to share three experiments of mine with this library for reading, writing XML and parsing a live RSS feed.

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Lucene by Example: Specifying Analyzers on a per-field-basis and writing a custom Analyzer/Tokenizer

Sunday, July 6th, 2014

Lucene is my favourite search engine library and the more often I use it in my projects the more features or functionality I find that were unknown to me.

Two of those features I’d like to share in the following tutorial is one the one hand the possibility to specify different analyzers on a per-field basis and on the other hand the API to create a simple character based tokenizer and analyzer within a few steps.

Finally we’re going to create a small index- and search application to test both features in a real scenario.

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Using jOOQ and Build Helper Plugin to Generate Database Metamodels with Maven

Tuesday, June 10th, 2014

When you need to derive meta-models from existing databases and want to create type-safe queries with an elegant, fluent-API, jOOQ definitely is a tool to consider here.

In the following tutorial I’d like to demonstrate how to integrate the jOOQ meta-model generator into a Maven build using the jOOQ Maven Plug-in, the Build Helper Maven Plug-in and Maven profiles to finally create a running application to query an existing RDBMS using such a generated meta-model.

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Java EE: Logging User Interaction the Aspect-Oriented Way using Interceptors

Monday, May 26th, 2014

Using dependency injection and aspect-oriented mechanisms like interceptors allow us to separate cross-cutting-concerns in our Java enterprise application, to control global aspects of our application and to avoid boilerplate code.

In the following short tutorial we’re going to create an aspect-oriented logger to protocol the initiating user, class and method called and the parameters passed to the method and finally we’re adding this interceptor to a sample RESTful web-service by adding a simple annotation.

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Using Java Config-Builder to assemble your Application Configuration

Tuesday, May 20th, 2014

There’s a variety of configuration frameworks to use in our Java applications. Java Config Builder is one of them and it offers some nice features that I would like to demonstrate in the following short examples as are:

Loading values from different sources like property-files, environment variables, command-line-arguments or system properties, specifying default values, mapping arbitrary types or collections, merging configurations and using the Java Bean Validation standard aka JSR-303.

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Allocating available random Ports in a Maven Build

Wednesday, May 7th, 2014

Recently in a project I encountered the following problem: The development team used Git with a branch-per-feature-like workflow and the integration server, Bamboo in this case, was configured not only to run the integration-tests for the master-branch but also for every change in a feature branch.

As the team  developed a Java EE web application ports like 8080 occasionally were already bound and builds failed.

I knew a plug-in for Jenkins CI I to search for available ports and assign them to a build variable but I wanted to control such information directly within the Maven build life-cycle so I searched and finally found Sonatype’s Port Allocator Plug-in for Maven.

In the following short example I’m going to demonstrate how to allocate available random ports in a Maven build and assign them to an embedded servlet container.

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Java Persistence API: Controlling the Second-Level-Cache

Monday, April 21st, 2014

Using the Java Persistence API and a decent persistence provider allows us to configure and fine-tune when and how the second level cache is used in our application.

In the following short examples, we’re going to demonstrate those features written as JUnit test cases and running on a H2 in-memory database.

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Using Apache Avro with Java and Maven

Saturday, March 8th, 2014

Apache Avro is a serialization framework similar to Google’s Protocol Buffers or Apache Thrift and offering features like rich data structures, a compact binary format, simple integration with dynamic languages and more.

In the following short five minute tutorial, we’re going to specify a schema to serialize books in a JSON format, we’re using the Avro Maven plugin to generate the stub classes and finally we’re serializing the data into a single file.

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Creating elegant, typesafe Queries for JPA, mongoDB/Morphia and Lucene using Querydsl

Thursday, February 13th, 2014

Querydsl is a framework that allows us to create elegant, type-safe queries for a variety of different data-sources like Java Persistence API (JPA) entities, Java Data Objects (JDO), mongoDB with Morphia, SQL, Hibernate Search up to Lucene.

In the following tutorial we’re implementing example queries for different environments – Java Persistence API compared with a JPQL and a criteria API query, mongoDB with Morphia and last but not least for Lucene.

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Creating Grammar Parsers in Java and Scala with Parboiled

Sunday, January 26th, 2014

Parboiled is a modern. lightweight and easy to use library to parse expression grammars in Java or Scala and in my humble opinion it is perfect for use cases where you need something between regular expressions and a complex parser generator like ANTLR.

In the following tutorial we’re going to create a simple grammar to specify a task list and write an implementation of a parser also as unit tests for each grammar rule in Java.

Additionally, we’re using the Scala variant of Parboiled to build up an Abstract Syntax Tree parser and analyze a given task list with it.

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JAX-RS 2.0 REST Client Features by Example

Monday, December 30th, 2013

JAX-RS 2.0 aka JSR 339 not also specifies the API to build up a RESTful webservice but also enhances the client side API to easen up the process of writing a client for a REST service.

In the following tutorial we’re building up a client for a ready-to-play REST service and explore the different new options e.g. how to handle requests in a synchronous or asynchronous way, how to add callback handlers for a request, how to specify invocation targets to build up requests for a later execution or how to filter the client-server communication using client request filters and client response filters.

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Creating a Websocket Chat Application with Vert.x and Java

Wednesday, November 13th, 2013

Vert.x is a modern, lightweight framework to build high performance applications running on the Java Virtual Machine. The framework is polyglot so that you’re able to write your application in Java, Groovy, Ruby, Python or even Javascript.

In addition it offers a nice component system, an actor-like concurrency model a distributed event bus and an elegant API to create scalable applications in no time.

In the following tutorial we’re going to build a websocket chat by creating a HTTP server and the websocket server using Vert.x, Java and Maven.

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Writing Java Integration Tests for MongoDB

Wednesday, October 16th, 2013

MongoDB is matured, document-oriented, cross-platform NoSQL database system with drivers available for a bunch of different programming languages.

In the following short examples I’m going to write some integration tests for MongoDB using the MongoDB Java driver and the Flapdoodle library to create an embedded MongoDB instance for testing.

We’re going to write tests for a simple persist-and-query scenarion and for a map-reduce function and in addition I’m going to show how to bind the start and stop of a MongoDB  instance to a Maven goal using the embedmongo-maven-plugin.

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Playing with Java 8 Lambda Expressions

Sunday, September 22nd, 2013

Many articles have been written about JSR 335 aka Lambda Expressions for the JavaTM Programming Language but I like to try new things out for myself and that’s why I’d like to share my snippets here.

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Business Process Modeling with Activiti and BPMN 2.0

Sunday, September 15th, 2013

Having tried a bunch of workflow engines and business processing management platforms I now have given the Activiti framework a try.

I immediately liked the good test support using annotations and jUnit test rules, a straight API and the good Eclipse IDE integration as well as I liked the Activiti Explorer and the Activiti REST Application and the feeling to achieve quick results with less effort when using this framework.

In the following tutorial I’m going to an example BPMN process for an issue request process using different components like Groovy script tasks, service tasks written in Java, E-Mail service tasks and form builders.

Finally I’m showing how to write a full integration test for the process and how to run the process in a web application environment using the Activiti Explorer application.

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Filtering Source Files using the Templating Maven Plugin

Tuesday, September 3rd, 2013

The Templating Maven Plugin looks useful if one needs to copy and to filter source files in a project e.g. to add property values from the build environment to a class.

For a short demonstration I’ve added the following short snippet.

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Creating a Chat Application using Java EE 7, Websockets and GlassFish 4

Tuesday, August 13th, 2013

Java EE 7 is out now and so I was curious to play around with the new specifications and APIs from in this technology stack.

That’s why I didn’t hesitate to add yet another websocket-chat tutorial to the existing ones on the internet in favor of gathering some experience with this technology and a possible integration using a GlassFish 4 server, the new Java API for JSON Processing for data serialization combined with custom websocket encoders/decoders and finally adding some Bootstrap and jQuery on the client side.

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Embedding Jetty or Tomcat in your Java Application

Tuesday, July 9th, 2013

Recently I needed to control an embedded web container from a Java application and I wanted to see how this could be achieved using an embedded instance of either Tomcat or Jetty here.

In the following short examples I would like to show how to embed both servers in an application in no  time using Gradle or Maven as build tool.

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Handling Feature Flags in a Java EE Application using Togglz

Wednesday, June 26th, 2013

Feature flags are a common technique, often combined with continuous deployment and delivery and they allow us to rollback a specific feature, to create A/B tests or to rollout a specific feature for a specific test group, a specific amount of users or dedicated systems.

In the following short examples I’d like you to demonstrate how easy it is to implement feature flags with the Togglz framework with a few steps in a Java EE environment.

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Creating and Packaging a Game in Java FX 2.2

Sunday, June 23rd, 2013

It’s been a long way for Java FX from the days of the F3 project the current release 2.2. Today there are many options how to create a Java FX application .. you may be using Java, Scala, Groovy or Visage, you may create your application in a programmatic way using the comfortable integrated builders or you may create your views using XML layouts and easy data-bindings with a few annotations.

If you need to bind your UI component properties to a specific application state, there’s a nice properties- and bindings API that makes your life easier.

In the following tutorial, I’m going to create a simple game application – one version using FXML templates, model- and controller classes and using external stylesheets – the other version as a programmatic version in one java class.

Finally I’m showing how easy it is to create a shippable application either as runnable jar or as Java Web Start/JNLP application by using Gradle and the Java FX Plugin for Gradle.

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Arquillian Transaction Extension: Transaction Rollback for your Java EE Integration Tests

Sunday, June 16th, 2013

I really love Arquillian to run integration tests for my Java EE applications – especially when running on different containers – and I also love the Arquillian tool stack from Arquillian Drone to the Arquillian Persistence Extensions.

Today I’d like to share a short snippet how to achieve transaction rollbacks when testing an EJB in combination with Arquillian and the Arquillian Transaction Extension…

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Continuous Deployment using GlassFish, Jenkins, Maven and Git

Wednesday, May 29th, 2013

Recently I needed a quick solution to deploy a Java EE 6 web application on a GlassFish instance automatically and subsequent to a successful build of the project on the integration server.

It took only a few steps using Jenkins, Maven and the Cargo plugin and I’d like to share this quick solution with you here.

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Creating Rich Clients with Apache Pivot

Sunday, May 19th, 2013

Apache Pivot is a modern framework to create rich clients as desktop applications or to run in a web browser.

It offers nice GUI elements, supports XML/WTKX templates, data bindings, JVM scripting languages and much more.

In the following short examples I’m going to create a desktop application to open a file browser, select a file and output the selected file’s name, first using a programmatic approach to create the user interface, and afterwards using XML/WTKX templates.

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Easy Database Migrations using Flyway, Java EE 6 and GlassFish

Sunday, April 28th, 2013

Database migrations often are a necessity in the application development and maintenance life-cycle.

Whenever we need to apply changes to the database structure, insert new data fragments and in doing so want to be sure that this all happens with some control and versioning.

The following tutorial shows how implement this for a simple Java EE 6 web application to be run on a GlassFish application server in a few quick steps using the Flyway framework, an eager initialized Singleton EJB and some Maven wiring.

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Creating slim Database Projections using JPA2 Constructor Expressions

Sunday, April 14th, 2013

One common question that you may encounter one day when using object-relational-mapping in your application is how to slim down data that you’re retrieving from the persistence layer down to a specific subset for your use-case in an efficient manner and without using complex additional mapping frameworks. In some situations you might declare lazy loaded fields but another approach that I’d like to share with you here are JPA2 constructor expressions.

Constructor expressions allow us to create plain old java objects from the result of an JPA query. The advantage is that we may use different projections for different scenarios and without being managed, the POJOs might help us save some resources here.

In the following tutorial, we’re going to persist 100 book entities with multiple properties to an embedded database and we’re using constructor expressions afterwards to create smaller POJOs using a subset of the information available from each persisted book.

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Micro Benchmarking your Tests using JUnit and JUnitBenchmarks

Sunday, March 10th, 2013

I recently stumbled upon a nice framework that allows to convert simple JUnit tests into micro benchmarks named JUnitBenchmarks.

It allows to set basic benchmark options and and to generate charts by adding some simple annotations and a test rule to your tests.

One might argue if it is wise to mix the aspects, testing and benchmarking and I’d agree for sure – nevertheless I think this framework can be handy sometimes so let’s create some benchmarks using JUnit and JUnitBenchmarks..

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Adding multiple EntityListeners to an Entity in JPA 2

Monday, February 25th, 2013

The ability to attach lifecycle events to an entity using simple annotations sometimes is a neat feature in the Java Persistence API.

The following short snippets demonstrate how to bind and trigger the different available lifecycle events using an embedded derby database and a bunch of annotations.

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Snippet: XML-Pull-Parser with XPP3

Friday, December 28th, 2012

When there is XML to be parsed sometimes we’re chosing a DOM parser, sometimes a SAX parser and sometimes we’re using an XML pull parser, especially on Android.

The following short snippet shows how to use the xpp3 xml pull parse to fetch some information in xml format from a public issue tracker and to extract issue details.

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Running categorized Tests using JUnit, Maven and Annotated-Test Suites

Thursday, December 6th, 2012

Sometimes we need to classify the tests in a project and a possible solution to achieve this goal is to assign different categories to the tests.

Often we’re doing this to separate the execution of fast-running and long-running tests or to run a specific set of tests that is only applicable in special situations.

To run a specific set of categorized tests there are different options and in the following tutorial we’ll be covering two of them: by configuring the Maven Surefire Plug-in or by using a JUnit Test Suite and the JUnit annotations.

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Content Detection, Metadata and Content Extraction with Apache Tika

Sunday, December 2nd, 2012

Encountering the situation that you want to extract meta-data or content from a file – might it be an office document, a spreadsheet or even a mp3 or an image – or you’d like to detect the content type for a given file then Apache Tika might be a helpful tool for you.

Apache Tika supports a variety of document formats and has a nice, extendable parser and detection API with a lot of built-in parsers available.

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New features in JUnit 4.11

Sunday, November 18th, 2012

JUnit is one of the most popular testing frameworks out there. Version 4.11 has just been released and offers some nice improvements that you shouldn’t miss.

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Creating an offline Rich-Client-Application using HTML, CSS and Java with SWT

Monday, November 12th, 2012

There are a lot of frameworks out there to create offline applications and rich clients in Java.

One exotic alternative is to use the HTML, CSS and Javascript for this purpose and render the application in a Java frame using SWT and SWT’s browser component.

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Make your Tests more readable with custom Hamcrest Matchers

Sunday, October 28th, 2012

Everyday we’re writing tests for our software and sometimes we’re in a situation where we’re testing a specific type or object very often.

Luckily Hamcrest allows us to create custom matchers by subclassing from a given variety of available matchers.

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HTML5 Server Send Events using Node.js or Jetty

Sunday, October 21st, 2012

The HTML5 working draft describes different techniques to push information from a server to the client and the one described in this tutorial are Server-Send Events (SSE).

Using Server-Send-Events eliminates the need to poll a server periodically for information using AJAX and is really easy to implement because of the simple specification and the fact that nearly all modern browsers already implement this specification.

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Lucene Snippets: Index Stats

Saturday, September 8th, 2012

In Lucene 4.x there is an API to fetch index statistics for specific document’s fields.

The following examples shows how to create an index with some random documents and fetch some statistics for a field afterwards ..

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Lucene Snippets: Faceting Search

Tuesday, August 28th, 2012

The latest snippet from my Lucene examples demonstrates how to achieve a facet search using the Lucene 4.0 API and how easy it is to define multiple category paths to aggregate search results for different possible facets.

In the following example we’re indexing some books as a classical example and create multiple category paths for author, publication date and category afterwards ..

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Jeah we’ve won the Atlassian Codegeist 2012 Competition – or – The return of the Pirate Ninja Unicorn

Sunday, August 12th, 2012

Atlassian Codegeist and Pirate Ninja Unicorn

Happy news for us, Theresa and I we’ve won the Atlassian Codegeist Competition 2012 with our Stash Readme Parser Plugin in the category: Best Stash Plugin.

Stash Readme Parser Plugin

We had two other plugins in the game, the Stash QR Code Plugin and the HTTP Request Workflow Function for Jira.

If you’re interested please take a look at the plugins in the Atlassian Marketplace our funny looking Pirate Ninja Unicorn Website or the project’s overview in my blog.

Resources

Creating a Windows Executable from a Jar using Maven

Tuesday, August 7th, 2012

Often in the life of a developer there is the need to create a windows executable for a Java application that is build and packaged in a Jar file.

The following short example shows how to create an executable Jar first and a windows executable containing vendor information, a nice icon and other stuff afterwards by using a combination of the Maven Shade Plugin and the launch4j Plugin for Maven.

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Integration Testing IMAP, SMTP and POP3 with GreenMail

Tuesday, July 31st, 2012

Having written some e-mail handling, sending or receiving library you’d like to run some integration tests against a real mail server?

Then GreenMail might help you out here .. the framework is not quite new on the market but it is really easy to setup IMAP,SMTP or POP3 services with it and it comes with some helpful libraries making your life a bit easier here.

That’s why I’ve come to the idea to share some examples for setting up different server instances, creating user accounts and – at last – fetching and validating e-mails…

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Aspects of Functional Programming in Java

Monday, July 16th, 2012

Functional programming is a trending topic these days and a lot of Java programmers are hot for the features that modern functional programming languages might offer.

Waiting for Java 8 and native closure support is a nice thing but for now we’re going to take a look at several Java frameworks that are trying to implement typical structures from those functional languages where possible using the capabilities of the Java language to emulate elements like higher-order-functions, closures, options and others …

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Task Scheduling in Java EE 6 on GlassFish using the Timer Service

Friday, June 22nd, 2012

Creating cronjobs or scheduled service executions is made really easy in Java EE 6. Scheduled tasks may be created in a programmatical style or simply by adding some annotations to an EJB.

In the following tutorial we’re creating some simple scheduled tasks and let them run on an embedded GlassFish instance using the Maven Embedded GlassFish plugin..

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Creating updatable Java Applications using Getdown and the Getdown Maven Plugin

Sunday, May 27th, 2012

Many programmers have suffered when trying to setup an environment to handle updates for their application without much effort. Some tried Java Web Start for this purpose and many encountered difficulties with this approach.

Now there is getdown that aims to replace Java Web Start by offering a simple architecture to handle updates that is fast, realiable and the only thing you need is a normal http server. Though getdown lets us handle our updates really easy it is possible to make this process even easier with the getdown maven plugin.

In the following example we’re building a simple swing application to be installed, updated and launched using getdown.

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Arquillian Tutorial: Writing Java EE 6 Integration Tests and more..

Thursday, April 26th, 2012

Now that the long awaited stable version of the Arquillian framework is released I wanted to demonstrate some interesting features of  this framework that really eases writing and running of integration tests for Java EE 6 applications in many different ways.

In the following tutorial we are going to create some real-world examples using Enterprise JavaBeans, Contexts and Dependency Injection, the Java Persistence API and we’re finally running Drone/Selenium tests against a JEE Web Application that is using Java Server Faces.

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Wiring made easy using OSGi Blueprint and Apache Karaf

Monday, April 16th, 2012

The OSGi Blueprint Container specification allows us to use dependency injection in our OSGi environment, declarative import and export of OSGi services, registering lifecycle listeners and wiring dependencies into our services with a few lines of XML code.
In the following tutorial we’re first building an OSGi bundle classical style and afterwards take a trip into the advantages of the Blueprint specification.

Our OSGi container of choice here will be Apache Karaf a lightweight container with a lot of nice features and – of course – blueprint enabled…

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Hibernate Search Faceting: Discrete and Range Faceting by Example

Monday, March 26th, 2012

In today’s tutorial we’re exploring the world of faceted searches like the one we’re used to see when we’re searching for an item on Amazon.com or other websites. We’re using Hibernate Search here that offers an API to perform discrete as well as range faceted searches on our persisted data.

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Snippet: Mixing Scala, Java in a Maven Project

Friday, March 23rd, 2012

Having just returned from the Atlassian Camp 2012 I just toyed around with Java and Scala and wanted to share the following snippet that demonstrates how to mix code from both languages in a Maven project using the maven-scala-plugin.

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Using the Android Fragment API in a Tablet App

Sunday, March 18th, 2012

Since I got a new tablet running Android 4.0 aka ice cream sandwich I wanted to play around a bit with the fragments API and creating an application for a tablet.

In the following tutorial, we’re going to build an application that renders several articles from a popular tech blog (just kidding) in a web view.

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Selenium WebDriver, Selenium Server and PageObjects by Example

Tuesday, March 6th, 2012

A lot has changed since Selenium RC and WebDriver has given us a new syntax to write tests for our web pages. PageObjects add an abstraction to the pages under test and finally we’re able to programatically start Selenium server instances and use them to run the tests.

In the following tutorial, we’re writing some tests using PageObjects, WebDriver, Selenium Server and finally we’re even taking some screenshots of our tested web pages..

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Ordering your JUnit Rules using a RuleChain

Tuesday, February 21st, 2012

JUnit Rules are a handy solution if one needs to alter test methods or wants to share common functionality between several test cases. JUnit 4.10 introduced a new class to order several rules according to our needs using a so called rule-chain.

In the following example, we’re going to create a simple custom rule and afterwards bind several instances of it in a specified order to a test method.

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JPA Persistence and Lucene Indexing combined in Hibernate Search

Sunday, February 5th, 2012

Often we’re writing an application that has to handle entities that – on the one side need to be persisted in a relational database using standards like the Java Persistence API (JPA) and using frameworks like Hibernate ORM or EclipseLink.

On the other side those entities and their fields are often stored in a highspeed indexer like Lucene. From this situation arises a bunch of common problems .. to synchronize both data sources, to handle special data mapped in an entity like an office document and so on..

Hibernate Search makes this all a lot easier for us as we’re hopefully going to see in the following short tutorial…

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Neo4j Graph Database Tutorial: How to build a Route Planner and other Examples

Friday, January 20th, 2012

Often in the life of developer’s life there is a scenario where using a relational database tends to get complicated or sometimes even slow – especially when there are fragments with multiple relationships or multiple connections present. This often leads to complex database queries or desperate software engineers trying to handle those problems with their ORM framework.

A possible solution might be to switch from a relational database to a graph database – and – neo4j is our tool of choice here. In the following tutorial we’re going to implement several examples to demonstrate the strengths of a graph database .. from a route planner to a social graph.

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Create Mobile Websites using Java Server Faces and PrimeFaces Mobile

Sunday, January 8th, 2012

The more smartphones and tablets are sold the bigger the need for a mobile version of a modern website. PrimeFaces Mobile helps us developers here  and allows us to quickly create mobile websites that display well on an iPhone, Android, Palm, Blackberry, Windows Mobile and others.

In the following tutorial we’re going to create a web application that is using Java Server Faces 2.1, PrimeFaces 3.1 and PrimeFaces Mobile 1.0 and runs on a simple web container like Tomcat or Jetty.

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Writing Styles and Themes on Android

Saturday, December 3rd, 2011

Using reusable styles and themes to modify an Android application’s look is really easy and helps to not violate thy DRY (don’t repeat yourself) principle by typing styles in every single UI element again and again.

In the following tutorial we’re going to write and apply some simple styles and a finally theme to a simple Android application.

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Managing Background Tasks on Android using the Alarm Manager

Sunday, November 27th, 2011

In today’s tutorial we’re going to take a look on how to handle periodically scheduled tasks on our Android device by using BroadcastReceivers, Services and the AlarmManager.

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Finding Memory Leaks using Eclipse and the MemoryAnalyzer Plugin

Wednesday, November 2nd, 2011

The MemoryAnalyzer Plugin for Eclipse allows us to quickly analyze heap dumps from a virtual machine and search for memory leaks. In the following tutorial we’re going to create and run a small application that is going to cause an OutOfMemoryException during its runtime.

In addition, we’re forcing the virtual machine to save a heap dump and finally analyzing this data using Eclipse and the MemoryAnalyzer plugin.

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Testing RESTful Web Services made easy using the REST-assured Framework

Sunday, October 23rd, 2011

REST-assured Integration Test Tutorial Logo There are many frameworks out there to facilitate testing RESTful webservices but there is one framework I’d like to acquaint you with my favourite framework named REST-assured.

REST-assured offers a bunch of nice features like a DSL-like syntax, XPath-Validation, Specification Reuse, easy file uploads and those features we’re going to explore in the following article.

With a few lines of code and Jersey I have written a RESTful web service that allows us to explore the features of the REST-assured framework and to run tests against this service.

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Maven Tomcat Plugin: Adding Authentication to an Embedded Tomcat

Wednesday, October 12th, 2011

The Tomcat Maven Plugin not only allows us to deploy our mavenized application to an existing Tomcat server but also to run our web application with an embedded instance from our project’s directory. Recently I needed to add basic authentication to such an instance and wanted to share the steps necessary here

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Android Widget Tutorial: Creating a screen-lock Widget in a few steps

Thursday, October 6th, 2011

hasCode Android Widget Tutorial Logo In today’s Android tutorial we’re going to take a look at Android’s Widget API and how to make a widget interact with a service using intents.

We’re going to create a fully functional application that allows us to enable or disable our smartphone’s screen lock settings using a widget that can be placed on our  home screen.

Finally I am going to show how to use a smartphone to test and debug our application and connect it to the IDE.

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Java EE 6 Development using the Maven Embedded GlassFish Plugin

Tuesday, September 20th, 2011

Today we’re going to take a look at the Maven Embedded GlassFish Plugin and how it allows us quick creation of GlassFish server instances in no time and Java EE 6 application deployment.

With a few lines of configuration in your Maven’s pom.xml we’ve got a running GlassFish instance and are able to  redeploy our application fast by pressing enter in our console.

In the following tutorial we’re going to build a Java EE 6 Web Application with a stateless session bean and a web servlet and finally deploy – and redeploy the application using the Maven GlassFish Plugin.

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REST-assured vs Jersey-Test-Framework: Testing your RESTful Web-Services

Monday, September 5th, 2011

Today we’re going to take a look at two specific frameworks that enables you to efficiently test your REST-ful services: On the one side there is the framework REST-assured that offers a nice DSL-like syntax to create well readable tests – on the other side there is the Jersey-Test-Framework that offers a nice execution environment and is built upon the JAX-RS reference implementation, Jersey.

In the following tutorial we’re going to create a simple REST service first and then implement integration tests for this service using both frameworks.

The title of this article might be misleading due to the fact that I am not going to compare both frameworks to choose a winner, just showing the different approach ..

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Screenscraping made easy using jsoup and Maven

Tuesday, August 30th, 2011

Sometimes in a developer’s life there is no clean API available to gather information from a web application .. no SOAP, no XML-RPC and no REST .. just a website hiding the information we’re looking for somewhere in its DOM hierarchy – so the only solution is screenscraping.

Screenscraping always leaves me with a bad feeling – but luckily there is a tool that makes this job at least a bit easier for a developer .. jsoup to the rescue!

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Contract-First Web-Services using JAX-WS, JAX-B, Maven and Eclipse

Tuesday, August 23rd, 2011

Using the contract-first approach to define a web service offers some advantages in contrast to the code-first approach.

In the following tutorial we’re going to take a look at some details of this approach and we’re going to implement a real SOAP service using JAX-WS, Maven and the Eclipse IDE.

Finally we’re going to run our service implementation on an embedded Jetty instance and we’re going to take a look at soapUI and how to test our service using this neat tool.

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Java EE 6, GlassFish and the Interceptor API

Wednesday, August 17th, 2011

Aspect oriented programming and the definition of cross-cutting-concerns is made easy in Java EE 6 using interceptors.

In the following tutorial we’re going to take a look at the different possibilities to apply interceptors to your EJBs at class or method level and how to setup a GlassFish instance to run the examples.

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Creating Portlets using Java Server Faces 2 and Liferay

Tuesday, July 19th, 2011

Portlets are a common technology to create plug&play components for modern web applications and are specified by the Java Community Process in several specification requests.

In the following tutorial we’re going to learn how to create custom portlets and how to deploy and embed them in Liferay, the popular open-source enterprise portal.

In addition we’re taking a look at inter-portlet-communication and how to create portlets using annotations.

Finally we’re building a portlet-state-aware Java-Server-Faces portlet using the  jsf-portlet-bridge mechanism.

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Integrating Groovy in your Maven builds using GMaven

Tuesday, July 12th, 2011

Often ant tasks are used in Maven builds but wouldn’t it be more attractive to integrate the Groovy language into our build process?

GMaven is the answers to this problem and brings together Maven and Groovy. It allows us to execute Groovy scripts inline from our Maven configuration, from a local script or even from a remote location. In the following short examples I am going to show how to configure Maven to execute Groovy scripts from different locations.

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Creating a LDAP server for your development environment in 5 minutes

Monday, June 13th, 2011

I am currently working on a plugin that needs to receive some information from an LDAP/Active Directory using JNDI. That’s why I needed to set up a directory server in a short time and I didn’t want to waste much effort for here.

Luckily for me the Apache Directory Studio saved my day and allowed me to set up everything I needed in a few minutes.

Short and sweet: In this tutorial I’m going to show you how to configure everything you need in your Eclipse IDE and finally how to query the created LDAP server with a tiny java client using JNDI.

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Message Driven Beans in Java EE 6

Sunday, June 5th, 2011

Message Driven Bean Tagcloud Message Driven Beans are no new concept due to the fact that they exist since EJB 2.0 but in Java EE 6 and the EJB 3.0 specification it is even more fun to use them.

In this tutorial we’re going to take a look at the specification and create an example application that transfers some objects via the Java Message Service to a Message-Driven Bean deployed on a GlassFish application server.

If you’re not interested in theory please skip to chapter 6 and directly start creating an application – otherwise we’ll begin with a short introduction into the JMS terminology and the concept of a Message-Driven-Bean..

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Oh JBehave, Baby! Behaviour Driven Development using JBehave

Tuesday, May 31st, 2011

Behaviour Driven Development Keyword Map

Behaviour Driven Development is the keyword when we’re talking about test scenarios written in an ubiquitous language, strong interaction with stakeholders, product owners or testers and well described, common understandable test scenarios.

The popular JBehave framework is our tool of choice here and allows us to decouple our test stories from the test classes, offers an integration for web tests using Selenium and finally there’s a helpful Maven plugin for JBehave, too.

After a short excursion into the principles of Behaviour Driven Development we’re going to write and implement test stories for simple acceptance tests and web tests using selenium.

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SCJP/OCPJP Exam Preparation: Pitfalls to avoid

Monday, April 25th, 2011

Last year I passed the exam for the “Oracle Certified Professional Java Programmer”successfully and wanted to share my exam preparation notes about common problems and pitfalls to be aware of.

That’s why I have added some code and examples for my top 25 challenges below.

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Mocking, Stubbing and Test Spying using the Mockito Framework and PowerMock

Sunday, March 27th, 2011


Today we’re going to take a look at the Mockito framework that not only does sound like my favourite summer cocktail but also offers nice testing, mocking/stubbing, test-spying features and mock injections.

After that we’re going to take a look on how to mock static or final classes by extending Mockito’s capabilities with PowerMock.

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Creating a sample Java EE 6 Blog Application with JPA, EJB, CDI, JSF and Primefaces on GlassFish

Tuesday, February 8th, 2011

Java EE 6 is out and it indeed offers an interesting stack of technologies. So in today’s tutorial we are going to build a small sample web application that builds on this stack using Enterprise JavaBeans, Java Persistence API, Bean Validation, CDI and finally Java Server Faces and PrimeFaces.

The application we’re going to develop is a simple blog app that allows us to create new articles, list them and – finally delete them. We’re also covering some additional topics like JSF navigation, i18n, Ajax-enabled components and the deployment on the GlassFish application server.
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Enterprise Java Bean / EJB 3.1 Testing using Maven and embedded Glassfish

Saturday, January 1st, 2011

Are you playing around with the shiny new 3.1 EJB API?

Using Maven for your Java projects?

Need an easy way to write and execute tests for your EJBs that depends on an Java Application Server?

No problem using Maven Archetypes, the Maven EJB Plugin and the GlassFish embedded Application Container..

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Bean Validation with JSR-303 and Hibernate Validator

Tuesday, December 14th, 2010

You want to add some validation logic to your Java beans? You want to achieve this with some shiny extendable annotations? Then give the Java Bean Validation standard aka JSR-303 a try..

We’re going to use the reference implementation for bean validation, Hibernate Validator in this tutorial but there are also links to other alternatives like Oval or Apache Bean Validation.

So let’s begin and validate some stuff ..
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Creating a REST Client Step-by-Step using JAX-RS, JAX-B and Jersey

Thursday, November 25th, 2010

Often in a developer’s life there is a REST service to deal with and nowadays one wants a fast and clean solution to create a client for such a service.

The following tutorial shows a quick approach using JAX-RS with its reference implementation, Jersey in combination with JAX-B for annotation driven marshalling between XML or JSON structures and our Java-Beans.

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Using PrimeFaces to pimp up existing Java Server Faces / JSF 2 Applications

Sunday, November 14th, 2010

In this tutorial we’re going to modify an existing Java Server Faces / JSF 2 web application by adding rich UI components to the existing layout.

Our tool of choice here is the PrimeFaces framework. It offers a wide range of interesting, customizable and (several) Ajax-enabled components that blend very well with JSF1+2  and also a solid documentation that allows a quick integration into existing projects.
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Object-relational Mapping using Java Persistence API / JPA 2

Monday, October 11th, 2010

Today we’re going to take a look at the world of object-relational Mapping and how it is done using the Java Persistence API by creating some basic examples, mapping some relations and querying objects using JPQL or the Criteria API..

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Creating a SOAP Service using JAX-WS Annotations

Thursday, September 23rd, 2010

It is possible to create SOAP webservices with only a few lines of code using the JAX-WS annotations. In a productivity environment you might prefer using contract-first instead of code-first to create your webservice but for now we’re going to use the fast method and that means code-first and annotations olé!

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How to create a simple Messaging Application using RabbitMQ 2 and Maven

Sunday, September 5th, 2010

Having read an interesting comparison by Lindenlabs evaluating modern message broker systems like ActiveMQ, ApacheQpid and amongst others – RabbitMQ – I wanted to take a quick look at the last one and built a small application producing and consuming some sample messages.

If you need some lecture on getting started with RabbitMQ or the key concepts of messaging I strongly recommend reading this list of introductional articles from the RabbitMQ homepage.

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Spring 3, Maven and Annotation Based Configuration

Sunday, August 22nd, 2010

There is still the urban myth that using Spring IoC container without thousands lines of XML code isn’t possible – so today we’re taking a look at annotation based configuration with Spring 3 and of course we’re using Maven..

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How to create a simple OSGi Web Application using Maven

Sunday, July 25th, 2010

In this tutorial we will take a look at the development of a simple OSGi Web Application and what tools can save us some time.

The Maven Bundle Plugin makes our life much easier here as does the OSGi Bundle Repository that offers some nice bundles – in our case the servlet API and an embedded Jetty web server.

So lets develop some bundles ..

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Java Server Faces/JSF 2 Tutorial – Step 1: Project setup, Maven and the first Facelet

Saturday, June 5th, 2010

In this short tutorial we are going to build a Java Server Faces Web-Application using JSF2.0, Facelets, Maven and Hibernate as ORM Mapper.

The goals for this first step are: Setting up the project structure using Maven, defining a frame template/decorator and a registration facelet, creating a managed bean and mapping it’s values to the facelet, adding some basic validation, displaying validation errors and finally adding a navigation structure.

In step2 of this tutorial we are going to add persistence using Hibernate, add some security, create a custom UI component and add some AJAX.

The Mojarra JSF implementation is used for this tutorial – perhaps I’m going to post more about the MyFaces implementation in another tutorial.

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Playing around with QR Codes

Tuesday, May 11th, 2010

Sometimes QR codes are a nice way to distribute information like calendar events, contact information, e-mail, geo-locations or internet addresses.

In the following article we’re going to encode information to QR code images using the ZXing library and afterwards decode information from a given QR code.

Finally we’re taking a look on online QR code generators and how to integrate the ZXing library in a Maven project.

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Signing APK with the Maven-Jar-Signer Plugin

Saturday, April 17th, 2010

There is a nice Maven plugin helping you signing your Android app – the Maven Jar Signer Plugin. If you want to learn more about Maven integration in an android project take a look at this article. (more…)

How to build a Confluence Macro Plugin

Tuesday, April 13th, 2010

The goal is to build a small macro plugin deployable via the Confluence plugin API rendering some spaces.

Please note that I am going to build the plugin using just Maven and not the Atlassian Maven Wrapper called the “Atlassian Plugin SDK” – more information about that is available at the Atlassian website.

The macro output will be rendered using a Velocity template and all messages are stored for i18n in properties files bundled with the plugin.

If you need to set up an instance of Confluence first, head over to this article. (more…)

Create a SOAP client using the JAX-WS Maven Plugin

Thursday, April 8th, 2010

Having written the article “How to build a Confluence SOAP client in 5 minutes” some readers asked me for some more information and help using the  JAX-WS plugin that I mentioned in the article instead of the Axis plugin – so here we go ;) (more…)

Manage dependencies with the Maven Dependency Plugin

Sunday, April 4th, 2010

In a maven project there are lots of dependencies to handle – often one wants to know which version of a software comes from.

The solution to this problem is the Maven Dependency Plugin which helps you to find used/unused/declared/undeclared dependencies in your project.

In addition the plugin allows you to copy or unpack artifacts. (more…)

Snippet: Simple One-Minute IMAP Client

Saturday, April 3rd, 2010

Building a simple IMAP Client that displays the subject of the messages in the “inbox” Folder using Maven (I just like Maven). (more…)

How to integrate Android Development Tools and Maven

Friday, April 2nd, 2010

With the Maven Android Plugin it is possible to build and deploy/undeploy your android app and start/stop the emulator – if you’re used to maven you won’t be going without it ;)

If you’re interested in signing your apk using maven – take a look at this article. (more…)

How to build a Confluence SOAP client in 5 minutes

Sunday, March 28th, 2010

In this tutorial we are going to build a SOAP client for the popular Confluence Wiki in about five minutes. The client is going to receive rendered HTML Markup from a specified Confluence Page.
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How to build a quick lucene search

Thursday, March 25th, 2010

Helo – today I wanted to post a small tutorial for a small index and search operation using the Lucene indexer and Maven for the project setup. (more…)

Review: "SCJP Sun Certified Programmer for Java 6 Study Guide"

Wednesday, March 24th, 2010

Short Facts:

  • About 850 pages – heavy weight – use it for self defence! ;)
  • Preparation material for the Sun Exam 310-065 (Sun Certified Java Programmer for Java SE 6)
  • CD-Rom with a nice exam simulator included
  • Authors: Kathy Sierry and Bert Bates
  • ISBN: 978-0071591065

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A look at Maven 3 alpha

Monday, March 22nd, 2010

We are all waiting for a stable release of Maven3 with following updates ..

  • faster, more performant .. save us time building our software and some precious memory ;)
  • improved artifact resolution api and plugin api
  • better osgi integration
  • a few bugfixes
  • no mixing of application dependencies and tooling dependencies
  • though it does not matter that much to me: polyglot features .. e.g.: “Writing your pom files in Groovy”
  • version-less parent elements for multi-module or multi-pom projects, no need to define the parent version in every submodule
  • better artifact resolution, which dependency or pom supplied which artifact to the outcome .. got that information from: “Splitter from the world of Java”

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How to add a local lib directory to Maven

Thursday, March 18th, 2010
Sometimes there is a dependency not available at a remote repository and one is too lazy to set up a local maven repository – that’s when one adds a directory in the project structure and wants maven to find dependencies there. (more…)
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