apply plugin: 'java'

task full_jar(type: Jar, dependsOn: classes) {
	manifest {
		attributes 'Main-Class': "${project.group}.Main"
	}
	from configurations.compile.collect {it.directory ? it : zipTree(it)}
	from files(compileJava)
	baseName = "${project.archivesBaseName}-full"
}

apply plugin: 'java'

task full_jar(type: Jar, dependsOn: classes) {
	manifest {
		attributes 'Main-Class': "${project.group}.Main"
	}
	from configurations.compile.collect {it.directory ? it : zipTree(it)}
	from compileJava.outputs.files.asPath
	baseName = "${project.archivesBaseName}-full"
}

build_gradle_jar_with_dependencies

Custom task using gradle java plugin for build runnable jar file with full dependencies set

Jar with dependencies task for build.gradle

java

Groovy