Generate java files in a gradle build using ragel.

build.gradle

abstract class Ragel extends DefaultTask {
    @InputFile
    abstract File inputFile
    @OutputFile
    abstract File outputFile
    @TaskAction
    void execute(InputChanges inputChanges) {
        project.exec {
            commandLine "ragel", "-J", "-o", outputFile, inputFile
        }
    }
};

def ragels = []
fileTree("src/main/ragel").matching {
    include "**/*.java.rl"
}.visit { input ->
    if ( input.directory ) return
    def ragel = task "${input.relativePath.toString().replaceAll("[/\\\\:<>\"?*|]", " ")}" (type:Ragel) {
        inputFile input.file.absoluteFile
        outputFile file("${buildDir}/generated-src/java/" + input.relativePath - ".rl")
    }
    ragels << ragel
}

compileJava {
  dependsOn ragels
  source = ['src/main/java', 'build/generated-src/java']
}