Java Mobile Edition Development Tools

Work In Progress

This is a guide to installing a complete development, testing, and packaging environment for Java MIDlets - applications for mobile devices - on Ubuntu Jaunty. It is also an attempt to confirm and define a completely open-source tool-set. In other words, it attempts to avoid any dependency on Sun Java Wireless Toolkit.

Free Open Source Overview

The FOSS (Free Open-Source Software) tools installed are:

The usual non-FOSS option is to use Sun's JWT (and most tool stacks expect it) instead of MicroEmulator and ProGuard.

Sun JWT is only available as 32-bit binary classes so to use it on a 64-bit host environment a 32-bit Java development kit would be needed alongside the default 64-bit JDK, and would only be used to launch the JWT tools.

The mix of licences for the various tools is mind-boggling, confusing, and enough to put you off. This is my current understanding of the situation but it may not be entirely accurate so do your own research - don't rely on me.

The Sun JWT preverifier has been  released under the GPL as part of the  PhoneMe project. MTJ can be configured with the location of the Sun JWT as part of the Antenna configuration but it will then use all the Sun JWT tools - free and non-free.

Recently however ProGuard has added a pre-verifier. MTJ has been modified sufficiently to be able to call an external pre-verifier using a defined command-line. That allows ProGuard to be used for pre-verification as well as for obfuscation. Antenna will use ProGuard (or RetroGuard) for obfuscation. MTJ expects ProGuard as the defined obfuscator.



Ensure OpenJDK is installed

sudo apt-get install openjdk-6-jdk

... and the default JVM

sudo update-alternatives --config java


Create a location to install Eclipse

sudo mkdir /usr/lib/eclipse-3.4

Download the latest Eclipse IDE for Java Developers from (~163MB).

Extract the file to the new location, removing the leading "eclipse/" from the file paths in the archive

sudo tar -xzf eclipse-jee-ganymede-SR2-linux-gtk-x86_64.tar.gz -C /usr/lib/eclipse-3.4 --strip-components 1

Startup Script

Create an updated and customised version of the Ubuntu Eclipse 3.2.x package start-up shell script. I've attached it Download for easy download. Rename it if necessary to work alongside the Ubuntu Eclipse package:

sudo wget --directory-prefix=/usr/bin
sudo chmod a+x /usr/bin/eclipse

Extension Locations

With the Eclipse start-up script in place it can be used to easily install Eclipse extensions outside of the main Eclipse installation directory. This is very useful since otherwise Eclipse can get over-loaded with unnecessary extensions when using some perspectives.

The first thing to do is ensure developers have permissions to install to the installation location. I generally will use /usr/local/lib/eclipse-$VERSION/ as the base path for extensions.

sudo mkdir -p /usr/local/lib/eclipse-3.4
sudo chown root:staff /usr/local/lib/eclipse-3.4

Add the user account(s) that will share the extensions to the staff group

sudo usermod -aG staff ${USER}

Note: The group membership won't become active until the next time the user logs on.

Mobile Toolkit for Java

Start eclipse with a custom location for the extension

/usr/bin/eclipse -ver 3.4 -configuration /usr/local/lib/eclipse-3.4/MTJ

The directory will be created by Eclipse. When Eclipse starts set the Workspace location then use Help > Software Updates... > Available Software > Add Site = (get this URL from the  MTJ Update sites page.

Give Eclipse a few seconds to read and parse the update site. If successful the dialog will be updated with the additional options. Select the MTJ.

Screenshot - Add MTJ extension

Press the Install... button then the Finish button and wait whilst the extension is downloaded and installed. Don't restart Eclipse at this point - press the No button and then exit Eclipse completely.

Check the extension was installed into the correct location

ls -l /usr/local/lib/eclipse-3.4/MTJ/eclipse/plugins/

Create a link to the extension in the main Eclipse installation:

sudo mkdir /usr/lib/eclipse-3.4/links
echo "path=/usr/local/lib/eclipse-3.4/MTJ" | sudo tee /usr/lib/eclipse-3.4/links/


Download from the  antenna web site and copy the jar file into a suitable location (which will be set in the Eclipse MTJ extension later). I put it in /usr/local/lib/


Download from the  web-site and extract the archive into /usr/local/lib/

tar -xzf microemulator-2.0.3.tar.gz -C /usr/local/lib


Download from the  web site and extract the archive into /usr/local/lib/

tar -xzf proguard4.3.tar.gz -C /usr/local/lib



Add some head-room to the user's default Java VM settings

echo -e "VMARGS=\"-Xms128m -Xmx512m -XX:PermSize=64M -XX:MaxPermSize=128M\"" >> ~/.eclipse/eclipserc

Mobile Toolkit for Java

Start Eclipse with the default installation location (this assumes the MTJ extension has been installed and linked as detailed previously)

/usr/bin/eclipse -ver 3.4

Select Window > Preferences > Java ME and set the Antenna location (/usr/local/lib/antenna-bin-1.1.0-beta.jar)

Screenshot - Java ME Antenna settings

Expand Java ME in the navigator pane and choose Device Management and press the Import... button.
Enter the location of MicroEmulator (/usr/local/lib/microemulator-2.0.3)

Screenshot - Java ME Import Devices

Expand Packaging in the navigator pane and choose Obfuscation. Set the ProGuard Root Directory (/usr/local/lib/proguard4.3)

Screenshot - Java ME Obfuscation

Choose Preverification in the navigator pane and set the command to run the default preverifier (java -jar /usr/local/lib/proguard4.3/lib/proguard.jar @/usr/local/lib/proguard4.3/

Screenshot - Java ME Preverification

Press the OK button to apply the changes and close the Preferences dialog.


Create a pre-verifier profile that can be used by Eclipse MTJ in the ProGuard base directory (here it is /usr/local/lib/proguard-4.3/). Notice that it relies upon external libraries provided by MicroEmulator so ensure the paths match the installed location since they are based on package versions.

-injars      in.jar
-outjars     out.jar
-libraryjars /usr/local/lib/microemulator-2.0.3/lib/midpapi20.jar
-libraryjars /usr/local/lib/microemulator-2.0.3/lib/cldcapi11.jar




 Creating deployable MIDlets with free software - François Kooman
 Developing for Mobiles with Java on Ubuntu - Liam Green-Hughes
 MTJ Getting Started
 Reasons to switch to the Eclipse Mobile Tools for Java
 p2: how I install plugins in extension locations... - Michael Scharf