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## note.0=[[rosjava/Anatomy of a RosJava Package|Anatomy of a RosJava Package]]
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## descriptive title for the tutorial
## title = Creating Rosjava Packages
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## description = Script wizards for conveniently creating rosjava packages and projects.
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== Overview ==

This tutorial will teach you how to use the `catkin_create_rosjava_xx` scripts to populate rosjava packages and subprojects. A typical workspace will look like (refer to [[rosjava/Anatomy of a RosJava Package|anatomy of a rosjava package]] for more details):

{{{
/src
  /rosjava_catkin_package_a
    /rosjava_gradle_subproject_a
    /rosjava_gradle_subproject_b
    /rosjava_gradle_subproject_c
  /rosjava_catkin_package_b
    /rosjava_gradle_subproject_d
    /rosjava_gradle_subproject_e
    /rosjava_gradle_subproject_f
}}}

== Preparation ==

You will need a [[rosjava/Tutorials/hydro/Installation|ros environment]] for your rosjava installation to utilise these scripts. Specifically, after installation (as described in the previous link), the example below will only work after running `source rosjava/devel/setup.bash` or something equivalent.

== RosJava Catkin Packages ==

Create an empty workspace and populate it with a couple of rosjava catkin packages:

{{{
> mkdir -p src
> cd src
> catkin_create_rosjava_pkg rosjava_catkin_package_a
> catkin_create_rosjava_pkg rosjava_catkin_package_b
> cd ..
> catkin_make
> source devel/setup.bash
}}}

At this point, there is nothing yet to compile, so catkin_make just configured a `setup.bash` for you. A single rosjava catkin package includes the following important files:

 * ''CMakeLists.txt'': configures gradle builds under the hood and sets up install rules.
 * ''package.xml'' : used to string/sequence compilation of separate gradle projects with catkin_make.
 * ''build.gradle'' : the (super) project gradle build rules customised for rosjava.
 * ''settings.gradle'' : the place to list all your subprojects (like CMake's add_subdirectory).

== RosJava Gradle Subprojects ==

=== Binary Projects (App) ===

Create a simple example application with talker and listener. 

{{{
> cd src/rosjava_catkin_package_a
> catkin_create_rosjava_project rosjava_gradle_subproject_a
> cd ../..
> catkin_make
}}}

For more details about java binary (app) projects, continue with the [[rosjava_build_tools/Tutorials/hydro/WritingPublisherSubscriber(Java)|Writing a Simple Publisher and Subscriber Tutorial]].

=== Library Project (Jar) ===

Create a simple library jar with a single compiled class, Dude. 

{{{
> cd src/rosjava_catkin_package_a
> catkin_create_rosjava_library_project rosjava_gradle_subproject_a
> cd ../..
> catkin_make
}}}

For more details about java library projects, continue with the [[rosjava_build_tools/Tutorials/hydro/Building RosJava Libraries|Building RosJava Libraries Tutorial]].

=== Message Projects (Msg) ===

With regards to creating msg projects, you might wish to read the rosjava documentation on how rosjava handles [[rosjava/Messages|messages]] and in particular [[rosjava/Tutorials/hydro/Unofficial Messages|unofficial message packages]].

== Faster Compiles ==

You can of course keep doing entire workspace recompiles every time you make an edit with catkin_make, but you can speed things up. Just as running ''make'' in build project folders for c++ will only make the targets you're interested in, you can do the same for rosjava with ''gradle''.

 * Source `devel/setup.bash` - this makes sure all the environment variables are correctly set.
 * From the root of your gradle super projects run './gradlew tasks' and pick the task you want to build (hint: check CMakeLists.txt).
 * From a gradle subprojects, use '../gradlew' instead.

== Video Tutorial ==
<<Youtube(lujgeInpejY)>>
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