How To Specify main class when using fatjar plugin in gradle.build

Question

I am interested in building a single jar containing all the module dependencies and external jars in a single executable jar file which I will be able to run with java -jar myApp.jar.

I have module A which is dependent on module B. Currently I'm using gradle, and my build.gradlescript looks like this:

    apply plugin: 'fatjar'
    description = "A_Project"
    dependencies {
      compile project(':B_Project')
      compile "com.someExternalDependency::3.0"
    }

When I build it through gradle command: clean build fatjar a fat jar 'A.jar' is created as expected. But running it with as I written above results in: no main manifest attribute, in A.jar How can I modify my build.gradle file and specify the main class, or the manifest?

Badge

No idea how to help You. It seems that command clean build fatjar has different outputs. Is that true? – Vela

See "Customization of MANIFEST.MF" in the Gradle User Guide. – Marla

Answer 1

I have figured it out myself: I've used uberjar Gradle task. now my build.gradle file looks like this:

apply plugin: 'java'
apply plugin: 'application'

mainClassName  = 'com.organization.project.package.mainClassName'

version = '1.0'

task uberjar(type: Jar) {
    from files(sourceSets.main.output.classesDir)
    from {configurations.compile.collect {zipTree(it)}} {
        exclude "META-INF/*.SF"
        exclude "META-INF/*.DSA"
        exclude "META-INF/*.RSA"
}

manifest {
    attributes 'Main-Class': 'com.organization.project.package.mainClassName'
    }
}


dependencies {
compile project(':B_Project')
compile "com.someExternalDependency::3.0"
}

and now I i use it with the command:

clean build uberjar

and it builds one nice runnable jar :)

Badge

i needed to add with jar below manifest to get the files in java/main/resources in the uberjar. Also inside collect is should be { it.isDirectory() ? it : zipTree(it) }... – Hauser

Answer 2

To get it working using fatjar, I added a manifest section in fatJar task:

task fatJar(type: Jar) {
    baseName = project.name + '-all'
    from { configurations.compile.collect { it.isDirectory() ? it : zipTree(it) } }
    with jar
    manifest {
        attributes 'Implementation-Title': 'Gradle Quickstart', 'Implementation-Version': version
        attributes 'Main-Class': 'com.organization.project.package.mainClassName'
    }
}

Retro