Maven - Nexus Demo

A Small demo how Manven and Nexus is working together.

Preparations

It is nice to have an IDE, such as IntelliJ, that can handle manen builds and profiles.

You should have Maven 3 and JDK8 installed on your local machine. Or use Docker Images, but all command assumes that you have it installed localy.

Start the servers.

I have prepared a Dockerfile to create a Jenkins Server image that can run Docker within Docker and a Docker Compose file that starts the two servers.

To start them, just run

docker-compose up

This starts Jenkins on http://localhost:8080. Pay attention to the initial password string. You need this to gain access to Jenkins the first time. I use admin/admin for this demo.

Nexus is started on http://localhost:8081 with default user/pass (admin/admin123).

The Demo

In this demo, I have used the artifact com.day.crx:crx-api:2.5.0. Nevermind what is does, I used it because it can not be found in the Central Repo. It is a part of the Adobe Experience Manager (AEM) toolbox. I just needed it for demo purposes.

Step 1 - Get it to build

Lets start with doing the command we all love.

mv clean install

It fails because we can't find that dependency. That one is deployed by Adobe in their repository that is found at https://repo.adobe.com/nexus/content/groups/public.

I have create a profile in the pom, abobe-public, that points out this repository.

Let us run the command, but this time with this profile activated.

``commandline mvn -Padobe-public clean install

Now it builds.

What is we wanted to use our local Nexus repository instead? The settings for that is done in the profile with id
_local-docker_. Let us try it. We need to remove the dependency from the local repo first. (The -U is to force update).

```commandline
rm -rf ~/.m2/repository/com/day/
mvn -U -Plocal-docker clean install

Nope, it doesn't work. That is because we have not added the Adobe Repository as a proxy to our local Nexus. Lets do that.

1. Login to Nexus as admin and click the little cog.
2. Select "Repositories"
3. Click "Create repository"
4. Select "maven2 (proxy)"
5. Enter "adobe-public-releases" as name
6. Enter "https://repo.adobe.com/nexus/content/groups/public" as URL.
7. Scroll down and hit "Create repository"
8. Select the "maven-public" repository.
9. Scroll down till you see the Member repositories and add the Adobe Repo to members.
10. Save

Now, go back to the Browse Repositories (that is the box and then Browse). You should see all our repositories now. If you look into the Adobe one, it should be empty.

Lets re-run the command.

mvn -U -Plocal-docker clean install

Now it works. If you browse the Adobe Repo in Nexus now, you will notice that it has downloaded it to the server with the dependencies needed. Now, the Adobe Repo can go down and we can still build our application.

Step 2 - Deploy it to Nexus

Nexus has two Maven repos by default; maven-releases and maven-snapshots. Let us try to deploy our artifact to the repo. The distribution management settings is done in the profile local-deploy.

mvn -Plocal-docker,local-deploy clean deploy

This fails... :( It failes because we don't have permissions to deploy to this server. You have to define the server credentials in the settings.xml file. That is normaly found under ~/.m2/settings.xml and you should encrypt the passwords. See https://maven.apache.org/guides/mini/guide-encryption.html.

I have created a settings.xml file with the default admin password to use. NEVER DO THIS IN REAL PROJECTS!!!

Run this command:

mvn -Plocal-docker,local-deploy -s settings.xml clean deploy

You can now browse the maven-snapshots repository at http://localhost:8081/#browse/browse:maven-snapshots.

Run the command again.

And again...

In a Snapshot Repository, you can redeploy an artifact.

Step 3 - Release

Change the version to 1.0.0 and run the deploy command.

If we browse the http://localhost:8081/#browse/browse:maven-releases, we now find the 1.0.0 version of our artifact.

Try running the command again.

Ooops!! Failed. You can not re-deploy something that is released.

Step 4 - Building this in Jenkins

You can point out this repository and make Jenkins build it. I do recommend that you fork it to your own repository so that you can do releases on you own without disturbing the original repository.