Chapter 1. Getting started with OpenIMAJ using Maven

Apache Maven is a project management tool. Maven performs tasks such as automatic dependency management, project packaging and more. We strongly encourage anyone using OpenIMAJ to use Maven to get their own project started. We’ve even provided a Maven archetype for OpenIMAJ (basically a project template) that lets you get started programming with OpenIMAJ quickly.

[Tip] Tip

You can find out more about Apache Maven at

OpenIMAJ requires Maven 2 or 3; if you want to build OpenIMAJ from source you will need Maven 3. You can check if you have Maven installed already by opening a terminal (or DOS command prompt) and typing:

mvn -version

If Maven is found the, version will be printed. If the version is less than 2.2.1, or Maven was not found, go to to download and install it. Once you’ve installed Maven try the above command to test that it is working.

To create a new OpenIMAJ project, run the following command:

mvn -DarchetypeCatalog= archetype:generate

Maven will then prompt you for some input. Firstly, when prompted, choose the openimaj-quickstart-archetype and choose the latest version. For the groupId, enter something that identifies you or a group that you belong to (for example, I might choose for personal projects, or org.openimaj for OpenIMAJ sub-projects). For the artifactId enter a name for your project (for example, OpenIMAJ-Tutorial01). The version can be left as 1.0-SNAPSHOT, and the default package is also OK. Finally enter Y and press return to confirm the settings. Maven will then generate a new project in a directory with the same name as the artifactId you provided.

[Note] Overriding the OpenIMAJ version

Versions of the archetype after 1.0.5 automatically select the corresponding OpenIMAJ version. With all versions of the archetype, you can override this by setting the openimajVersion on the command-line with the -D argument.

The project directory contains a file called pom.xml and a directory called src. The pom.xml file describes all of the dependencies of the project and also contains instructions for packaging the project into a fat jar that contains all your project code and resources together with the dependencies. If you find that you need to add another library to your project, you should do so by editing the pom.xml file and adding a new dependency. The src directory contains the code for your project. In particular, src/main/java contains your java application code and src/test/java contains unit tests.

The default project created by the archetype contains a small hello world application. To compile and assemble the hello world application you cd into the project directory from the command line (replacing OpenIMAJ-Tutorial01 with the name of your project):

cd OpenIMAJ-Tutorial01

and run the command:

mvn assembly:assembly

This will create a new directory called target that contains the assembled application jar (the assembled jar is the one whose name ends with -jar-with-dependencies.jar). To run the application, enter:

java -jar target/OpenIMAJ-Tutorial01-1.0-SNAPSHOT-jar-with-dependencies.jar

The application will then run, and a window should open displaying a picture with the text hello world. Closing the window, or ctrl-c on the command line, will quit the application.

OpenIMAJ Hello World

1.1. Integration with your favourite IDE

We could now go ahead and start playing with the code in a text editor, however this really isn’t recommended! Using a good Integrated Development Environment (IDE) with auto-completion will make your experience much better.

Maven integrates with all the popular IDEs. The OpenIMAJ developers all use Eclipse so that is what we’re most familiar with, however we should be able to help getting it set up in a different IDE if you wish.

Integration with Eclipse is quite simple. From the command line, inside the project directory, issue the command:

mvn eclipse:eclipse

This will generate Eclipse project files in the same directory. In Eclipse you can then import the project into the Eclipse workspace (File > import..., choose Existing projects into workspace, select the project directory, make sure Copy projects into workspace is unchecked, then click Finish). The project should then appear in the workspace and you’ll be able to look at the file that was generated by the archetype.

IMPORTANT By default Eclipse doesn’t know about Maven and its repositories of jars. When you first import an OpenIMAJ project into Eclipse it will have errors. You can fix this by adding a new Java classpath variable (Eclipse > Preferences > Java > Build Path > Classpath Variables) called M2_REPO. The value of this variable is the location of your .m2/repository directory. For Unix systems this is usually found in your home directory, for Windows systems it is found in C:\Documents and Settings\<user>\.

Eclipse classpath variables

Once you’ve opened the file in Eclipse, you can right-click on it and select Run as > Java Application to run it from within Eclipse.

Eclipse Run as...