How to deploy Maven projects to Artifactory with GitLab CI/CD

Introduction

In this article, we will show how you can leverage the power of GitLab CI/CD to build a Maven project, deploy it to Artifactory, and then use it from another Maven application as a dependency.

You'll create two different projects:

simple-maven-dep: the app built and deployed to Artifactory (available at https://gitlab.com/gitlab-examples/maven/simple-maven-dep )
simple-maven-app: the app using the previous one as a dependency (available at https://gitlab.com/gitlab-examples/maven/simple-maven-app )

We assume that you already have a GitLab account on GitLab.com, and that you know the basic usage of Git and GitLab CI/CD. We also assume that an Artifactory instance is available and reachable from the internet, and that you have valid credentials to deploy on it.

Create the simple Maven dependency

First of all, you need an application to work with: in this specific case we will use a simple one, but it could be any Maven application. This will be the dependency you want to package and deploy to Artifactory, in order to be available to other projects.

Prepare the dependency application

For this article you'll use a Maven app that can be cloned from our example project:

Log in to your GitLab account
Create a new project by selecting Import project from ➔ Repo by URL

Add the following URL:

https://gitlab.com/gitlab-examples/maven/simple-maven-dep.git

Click Create project

This application is nothing more than a basic class with a stub for a JUnit based test suite. It exposes a method called hello that accepts a string as input, and prints a hello message on the screen.

The project structure is really simple, and you should consider these two resources:

pom.xml: project object model (POM) configuration file
src/main/java/com/example/dep/Dep.java: source of our application

Configure the Artifactory deployment

The application is ready to use, but you need some additional steps to deploy it to Artifactory:

Log in to Artifactory with your user's credentials.
From the main screen, click on the libs-release-local item in the Set Me Up panel.
Copy to clipboard the configuration snippet under the Deploy paragraph.
Change the url value in order to have it configurable via variables.

Copy the snippet in the pom.xml file for your project, just after the dependencies section. The snippet should look like this:

<distributionManagement>
  <repository>
    <id>central</id>
    <name>83d43b5afeb5-releases</name>
    <url>${env.MAVEN_REPO_URL}/libs-release-local</url>
  </repository>
</distributionManagement>

Another step you need to do before you can deploy the dependency to Artifactory is to configure the authentication data. It is a simple task, but Maven requires it to stay in a file called settings.xml that has to be in the .m2 subdirectory in the user's homedir.

Since you want to use GitLab Runner to automatically deploy the application, you should create the file in the project's home directory and set a command line parameter in .gitlab-ci.yml to use the custom location instead of the default one:

Create a folder called .m2 in the root of your repository
Create a file called settings.xml in the .m2 folder

Copy the following content into a settings.xml file:

<settings xsi:schemaLocation="http://maven.apache.org/SETTINGS/1.1.0 http://maven.apache.org/xsd/settings-1.1.0.xsd"
    xmlns="http://maven.apache.org/SETTINGS/1.1.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <servers>
    <server>
      <id>central</id>
      <username>${env.MAVEN_REPO_USER}</username>
      <password>${env.MAVEN_REPO_PASS}</password>
    </server>
  </servers>
</settings>

Username and password will be replaced by the correct values using variables.

Configure GitLab CI/CD for `simple-maven-dep`

Now it's time we set up GitLab CI/CD to automatically build, test and deploy the dependency!

GitLab CI/CD uses a file in the root of the repo, named .gitlab-ci.yml, to read the definitions for jobs that will be executed by the configured GitLab Runners. You can read more about this file in the GitLab Documentation.

First of all, remember to set up variables for your deployment. Navigate to your project's Settings > CI/CD > Variables page and add the following ones (replace them with your current values, of course):

MAVEN_REPO_URL: http://artifactory.example.com:8081/artifactory (your Artifactory URL)
MAVEN_REPO_USER: gitlab (your Artifactory username)
MAVEN_REPO_PASS: AKCp2WXr3G61Xjz1PLmYa3arm3yfBozPxSta4taP3SeNu2HPXYa7FhNYosnndFNNgoEds8BCS (your Artifactory Encrypted Password)

Now it's time to define jobs in .gitlab-ci.yml and push it to the repo:

image: maven:latest

variables:
  MAVEN_CLI_OPTS: "-s .m2/settings.xml --batch-mode"
  MAVEN_OPTS: "-Dmaven.repo.local=.m2/repository"

cache:
  paths:
    - .m2/repository/
    - target/

build:
  stage: build
  script:
    - mvn $MAVEN_CLI_OPTS compile

test:
  stage: test
  script:
    - mvn $MAVEN_CLI_OPTS test

deploy:
  stage: deploy
  script:
    - mvn $MAVEN_CLI_OPTS deploy
  only:
    - master

GitLab Runner will use the latest Maven Docker image, which already contains all the tools and the dependencies you need to manage the project, in order to run the jobs.

Environment variables are set to instruct Maven to use the homedir of the repo instead of the user's home when searching for configuration and dependencies.

Caching the .m2/repository folder (where all the Maven files are stored), and the target folder (where our application will be created), is useful for speeding up the process by running all Maven phases in a sequential order, therefore, executing mvn test will automatically run mvn compile if necessary.

Both build and test jobs leverage the mvn command to compile the application and to test it as defined in the test suite that is part of the application.

Deploy to Artifactory is done as defined by the variables we have just set up. The deployment occurs only if we're pushing or merging to master branch, so that the development versions are tested but not published.

Done! Now you have all the changes in the GitLab repo, and a pipeline has already been started for this commit. In the Pipelines tab you can see what's happening. If the deployment has been successful, the deploy job log will output:

[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 1.983 s

Note: the mvn command downloads a lot of files from the internet, so you'll see a lot of extra activity in the log the first time you run it.

Yay! You did it! Checking in Artifactory will confirm that you have a new artifact available in the libs-release-local repo.

Create the main Maven application

Now that you have the dependency available on Artifactory, it's time to use it! Let's see how we can have it as a dependency to our main application.

Prepare the main application

We'll use again a Maven app that can be cloned from our example project:

Create a new project by selecting Import project from ➔ Repo by URL

Add the following URL:

https://gitlab.com/gitlab-examples/maven/simple-maven-app.git

Click Create project

This one is a simple app as well. If you look at the src/main/java/com/example/app/App.java file you can see that it imports the com.example.dep.Dep class and calls the hello method passing GitLab as a parameter.

Since Maven doesn't know how to resolve the dependency, you need to modify the configuration:

Go back to Artifactory
Browse the libs-release-local repository
Select the simple-maven-dep-1.0.jar file
Find the configuration snippet from the Dependency Declaration section of the main panel

Copy the snippet in the dependencies section of the pom.xml file. The snippet should look like this:

<dependency>
  <groupId>com.example.dep</groupId>
  <artifactId>simple-maven-dep</artifactId>
  <version>1.0</version>
</dependency>

Configure the Artifactory repository location

At this point you defined the dependency for the application, but you still miss where you can find the required files. You need to create a .m2/settings.xml file as you did for the dependency project, and let Maven know the location using environment variables.

Here is how you can get the content of the file directly from Artifactory:

From the main screen, click on the libs-release-local item in the Set Me Up panel
Click on Generate Maven Settings
Click on Generate Settings
Copy to clipboard the configuration file
Save the file as .m2/settings.xml in your repo

Now you are ready to use the Artifactory repository to resolve dependencies and use simple-maven-dep in your main application!

Configure GitLab CI/CD for `simple-maven-app`

You need a last step to have everything in place: configure the .gitlab-ci.yml file for this project, as you already did for simple-maven-dep.

You want to leverage GitLab CI/CD to automatically build, test and run your awesome application, and see if you can get the greeting as expected!

All you need to do is to add the following .gitlab-ci.yml to the repo:

image: maven:latest

stages:
  - build
  - test
  - run

variables:
  MAVEN_CLI_OPTS: "-s .m2/settings.xml --batch-mode"
  MAVEN_OPTS: "-Dmaven.repo.local=.m2/repository"

cache:
  paths:
    - .m2/repository/
    - target/

build:
  stage: build
  script:
    - mvn $MAVEN_CLI_OPTS compile

test:
  stage: test
  script:
    - mvn $MAVEN_CLI_OPTS test

run:
  stage: run
  script:
    - mvn $MAVEN_CLI_OPTS package
    - mvn $MAVEN_CLI_OPTS exec:java -Dexec.mainClass="com.example.app.App"

It is very similar to the configuration used for simple-maven-dep, but instead of the deploy job there is a run job. Probably something that you don't want to use in real projects, but here it is useful to see the application executed automatically.

And that's it! In the run job output log you will find a friendly hello to GitLab!

Conclusion

In this article we covered the basic steps to use an Artifactory Maven repository to automatically publish and consume artifacts.

A similar approach could be used to interact with any other Maven compatible Binary Repository Manager. Obviously, you can improve these examples, optimizing the .gitlab-ci.yml file to better suit your needs, and adapting to your workflow.