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To Build with Catkin or Gradle

This tutorial provides some information on the different build methods for rosjava packages - these are catkin_make and the gradle wrapper.

Overview

A typical workspace will look like (refer to 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

The best way of understanding the usefulness of both build commands is to understand their scope. In the above workspace, catkin_make has scope across the whole workspace - it is responsible for linking and sequencing each catkin package/gradle (super)project. The gradle wrapper on the other hand only has scope within a single catkin package.

When to Use Catkin Make

Catkin make is useful in the following situations:

• A first build of your entire workspace since it creates the setup.bash and is a one-shot way of building the entire workspace.
• Continuous integration builds.

If we didn't have catkin packages linking the gradle projects, you'd need to compile each by hand, one by one, or have a bash script to do so for you.

When to Use the Gradle Wrapper

You can use catkin_make exclusively, but that can be annoyingly slow as it's running through the entire workspace. Just as for c++ catkin builds (where you use make), you can drop down a level and directly use the gradle wrapper to compile single gradle projects, or even subprojects.

Compiling a binary app subproject:

> source devel/setup.bash
> cd src/rosjava_catkin_package_a/my_pub_sub_tutorial
> ../gradlew installApp

Compiling a library subproject:

> source devel/setup.bash
> cd src/rosjava_catkin_package_a/my_java_library
> ../gradlew publishMavenJavaPublicationToMavenRepository