Gradle Build Description

2018-06-15 Jesper Öqvist Lund University, Sweden

This is a repackaging of Görel Hedins State Machine example to use a Gradle build instead of the Ant build of the original example project.

The advantages of using Gradle over Ant are:

• More flexibility in the builds by using Groovy code in the build tasks.
• Dependencies can be automatically downloaded from Maven repositories.
• Improved handling of file dependencies between build tasks.
• Build by convention: similar to Maven, Gradle assumes some sane default settings which minimizes the amount of configuration you need to do for each build.

In order to support building JastAdd projects with Gradle, a custom Gradle plugin, JastAddGradle, is used. The plugin is published to the JastAdd Maven repository (http://jastadd.org/mvn/).

Directory Structure

In order to make the state machine project a bit better structured the source directories have been reorganized in the following manner:

• src/main the main Java sources (includes StateMachine compiler)
• src/test the Java test sources
• src/gen destination for generated Java code, removed by gradle clean
• build temporary directory used by Gradle for build artifacts, removed by gradle clean

Note that the exampleprogs directory moved into src/main and the tests directory moved into src/test.

No additional Jar libraries are needed in the project from scratch since the Gradle build fetches the required libraries dynamically. Thus, the tools directory has been removed.

The Build Script

There are two new files used by the Gradle build:

• build.gradle the gradle build script
• jastadd_modules the JastAdd module definitions

The jastadd_modules file looks like this:

module("statemachine") {
    java {
        basedir "."
        include "main/**/*.java"
        include "gen/**/*.java"
    }

    jastadd {
        include "spec/*.ast"
        include "spec/*.jadd"
        include "spec/*.jrag"
    }

    scanner {
        include "spec/*.flex"
    }

    parser {
        include "spec/*.parser"
    }
}

This is a list of the files used by the parser, scanner and attribute code generators. The JastAddGradle plugin uses these lists to run the various code generators.

The build.gradle script is a little more complicated. It starts by listing Gradle plugin dependencies:

plugins {
  id 'java'
  id 'maven'
  id 'org.jastadd' version '1.13.0'
}

The java and maven plugins are default Gradle plugins, and the org.jastadd plugin is our custom JastAddGradle plugin.

The next part of the build script configures the JastAddGradle plugin by telling it where to search for modules, which module to build, and some other important build parameters:

jastadd {
  configureModuleBuild()

  modules "jastadd_modules"
  module = "statemachine"

  astPackage = "AST"
  parser.name = "StateMachineParser"
}

The JastAddGradle plugin adds default tasks to generate the scanner, parser, and the abstract grammar. The remaining parts of the build script are typical for a Java Gradle build.

Testing

You can run the tests using the following command:

gradle test

The above runs the tests located in the src/test/tests directory. The followig creates the Jar file GradleBuild-all.jar.

gradle jarAll

Run the generated Jar file using this command:

java -jar GradleBuild-all.jar exampleprogs/test.sm