There is a case we want to appened Git-Commit-Id to our Jar file name or RPM file, and we may need read that information in our Application.

When using Maven, we can use git-commit-id-plugin, I have document it in previous post. Now, I have switched to Gradle, unlucky, I didn’t find a mature plugin to do the same function.

General Idea

We can learn from git-commit-id-plugin, and try to wirte some simple task to achieve similiar function. The general idea is, generate a properties file under class path, while Maven/Gradle building process, write Git information to that properties file. Then this properties will be packaged in Jar file.

Grgit

Grgit is a wrapper over JGit that provides a fluent API for interacting with Git repositories in Groovy-based tooling.

with grgit we will be able to read Git information in Gradle. I just need very simple feature from grgit, so used a old version 1.1.0

I defined grgit in my parent build.gradle, and store in gloable variable for all the sub modules.

buildscript {
    repositories {
    	maven {
      		url "https://plugins.gradle.org/m2/"
    	}
    }

    dependencies {
        classpath "org.ajoberstar:grgit:1.1.0"
    }
}

ext {
	// Open the Git repository in the current directory.
    git = org.ajoberstar.grgit.Grgit.open(file('.'))
    // Get commit id of HEAD.
    gitRevision = git.head().id
    // Get abbreviated commit Id of HEAD
    gitAbbRevision = git.head().abbreviatedId
}

Use Git-Id in Jar file

As we already get Git-Id in parent build.gradle, in sub module build.gradle file, just need assign the value to VERSION variable.

version="${project.version}-${gitAbbRevision}"

Use Git-Id in RPM file

Similiar to Jar file, I use nebula-gradle-ospackage to build RPM files. Just change the VERSION in similar way.

 ospackage {
    packageName = "${project.name}"
    version = "${project.version}-${gitAbbRevision}"
    release = '1'
    arch = I386
    os = LINUX
}

Write Git-Id to Properties File

Haven’t really familiar with Groovy, this code must be quite stupid and foolish, but it’s working :) Let’s improve it later.

task getVersions(dependsOn: processResources) {
    doLast {
    	def separator = System.getProperty('line.separator')
        def version = project.version.toString()
        boolean success = new File("$buildDir/resources/main/version.properties").delete()
        def file = new File("$buildDir/resources/main/version.properties")
		//file.write("project.version=${version}$separator")
        file << "project.version=${moduleVersion}$separator"
        file << "git.version=${gitRevision}$separator"
        file << "git.abbreviated.version=${gitAbbRevision}$separator"
    }
}

classes {
    dependsOn getVersions
}

As we set task dependencies, no need to manually invoke getVersions method, while we building classes, it will automatically generated.

Now you can read this version.properties in your application, and use it as your like.