using-nexus-with-gradle.md

Using Nexus with Gradle

Configuring Gradle to download artifacts from Nexus instead of Maven Central will, most of the time, not only speed up build processes by caching commonly used dependencies but also help ensuring reproducible builds, since one only depends on their Nexus availability and not the public repositories.

Gradle can also be configured to upload artifacts to Nexus, enabling the management of artifacts private to an organization.

Downloading artifacts from Nexus

In order to enable Gradle to to download artifacts from Nexus, one is to add the following to build.gradle:

repositories {
    maven {
        url "${nexusUrl}/repository/maven-public/"
    }
}

Also, one may often find mavenCentral() statements scattered around existing build.gradle files. As a rule of the thumb, one should replace it with something like:

maven {
    url "${nexusUrl}/repository/maven-public/"
}

Finally, one must set nexusUrl either in the project-local gradle.properties file or in the global ~/.gradle/gradle.properties file:

nexusUrl=https://nexus.example.com

Uploading artifacts to Nexus

In order to upload private artifacts to Nexus, one must use the maven-publish plugin and configure the publishing extension as follows:

apply plugin: 'maven-publish'

publishing {
    publications {
        maven(MavenPublication) {
            artifactId '<custom-artifact-id>'
            from components.java
            groupId '<custom-group-id>'
            version project.version
        }
    }
    repositories {
        maven {
            credentials {
                username nexusUsername
                password nexusPassword
            }
            if (!project.version.endsWith('-SNAPSHOT')) {
                url "${nexusUrl}/repository/maven-releases"
            } else {
                url "${nexusUrl}/repository/maven-snapshots"
            }
        }
    }
}

Then, to upload built artifacts to Nexus, one is to run:

$ gradle publish

Note: one must define their Nexus credentials in gradle.properties:

nexusUrl=https://nexus.example.com
[email protected]
nexusPassword=s4f3#p4ssw0rd!

Attention: If GCP IAM authentication is enabled, username and password are not the GCP organization credentials.

Encrypting credentials

Note: Encrypting credentials is a security best-pratice.

Although Gradle doesn't provide a built-in way to encrypt credentials, there's a Gradle plugin which may come in handy. To use it, one must add the following to build.gradle:

plugins {
    id 'nu.studer.credentials' version '1.0.3'
}

Then, add their Nexus password to the plugin's "keychain":

./gradlew addCredentials -PcredentialsKey="encryptedNexusPassword" -PcredentialsValue="<the-nexus-password>"

and adjust build.gradle accordingly:

def nexusPassword = credentials.encryptedNexusPassword

publishing {
    publications {
        maven(MavenPublication) {
            artifactId '<custom-artifact-id>'
            from components.java
            groupId '<custom-group-id>'
            version project.version
        }
    }
    repositories {
        maven {
            credentials {
                username nexusUsername
                password nexusPassword
            }
            if (!project.version.endsWith('-SNAPSHOT')) {
                url "${nexusUrl}/repository/maven-releases"
            } else {
                url "${nexusUrl}/repository/maven-snapshots"
            }
        }
    }
}

Attention: If GCP IAM authentication is enabled, username and password are not the GCP organization credentials.