How to make gradle download dependencies without actually building things

Question

On a new environment gradle build takes quite a while because all dependencies have to be downloaded.

Is there a way to only download dependencies in order to speed up the following build?

That way we could for example already prefill a CI build environment.

Answer 1

Edit: Updated for Gradle 6+.

Some notes:

• This new approach downloads jars into a folder, and then deletes the folder. So the result of having the jars in the Gradle cache is a side-effect.
• It currently uses jars configured for the main source-set but could be generalized.
• Even though it is neither efficient nor elegant, it can be useful if you actually want the jars (and transitive dependencies): simply comment-out the deletion of the runtime folder.

This solution can be handy when you want the jars (and transitive dependencies), as you simply have to comment-out deleting the folder.

Consider this build.gradle (as an arbitrary, concrete example):

apply plugin: 'java'

dependencies {
    implementation 'org.apache.commons:commons-io:1.3.2'
    implementation 'org.kie.modules:org-apache-commons-lang3:6.2.0.Beta2'
}

repositories { 
   jcenter()
}

task getDeps(type: Copy) {
    from sourceSets.main.runtimeClasspath
    into 'runtime/'

    doFirst {
        ant.delete(dir: 'runtime')
        ant.mkdir(dir: 'runtime')
    }

    doLast {
        ant.delete(dir: 'runtime')
    }
}

Example run:

$ find /Users/measter/.gradle/caches -name "commons-io*1.3.2.jar"

$ gradle getDeps

$ find /Users/measter/.gradle/caches -name "commons-io*1.3.2.jar"
/Users/measter/.gradle/caches/modules-2/files-2.1/commons-io/commons-io/1.3.2/[snip]/commons-io-1.3.2.jar

Answer 2

I've found ./gradlew dependencies (as suggested by this user) to be very handy for Docker builds.