debian-mirror-gitlab/doc/user/packages/maven_repository/index.md

---
stage: Package
group: Package
info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#assignments
---

# Maven packages in the Package Repository

> - [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/5811) in [GitLab Premium](https://about.gitlab.com/pricing/) 11.3.
> - [Moved](https://gitlab.com/gitlab-org/gitlab/-/issues/221259) to GitLab Core in 13.3.

Publish [Maven](https://maven.apache.org) artifacts in your project’s Package Registry.
Then, install the packages whenever you need to use them as a dependency.

## Build a Maven package

This section explains how to install Maven and build a package.

If you already use Maven and know how to build your own packages, go to the
[next section](#authenticate-to-the-package-registry-with-maven).

Maven repositories work well with Gradle, too. To set up a Gradle project, see [get started with Gradle](#build-a-java-project-with-gradle).

### Install Maven

The required minimum versions are:

- Java 11.0.5+
- Maven 3.6+

Follow the instructions at [maven.apache.org](https://maven.apache.org/install.html)
to download and install Maven for your local development environment. After
installation is complete, verify you can use Maven in your terminal by running:

```shell
mvn --version
```

The output should be similar to:

```shell
Apache Maven 3.6.1 (d66c9c0b3152b2e69ee9bac180bb8fcc8e6af555; 2019-04-04T20:00:29+01:00)
Maven home: /Users/<your_user>/apache-maven-3.6.1
Java version: 12.0.2, vendor: Oracle Corporation, runtime: /Library/Java/JavaVirtualMachines/jdk-12.0.2.jdk/Contents/Home
Default locale: en_GB, platform encoding: UTF-8
OS name: "mac os x", version: "10.15.2", arch: "x86_64", family: "mac"
```

### Create a project

Follow these steps to create a Maven project that can be
published to the GitLab Package Registry.

1. Open your terminal and create a directory to store the project.
1. From the new directory, run this Maven command to initialize a new package:

   ```shell
   mvn archetype:generate -DgroupId=com.mycompany.mydepartment -DartifactId=my-project -DarchetypeArtifactId=maven-archetype-quickstart -DinteractiveMode=false
   ```

   The arguments are:

   - `DgroupId`: A unique string that identifies your package. Follow
   the [Maven naming conventions](https://maven.apache.org/guides/mini/guide-naming-conventions.html).
   - `DartifactId`: The name of the `JAR`, appended to the end of the `DgroupId`.
   - `DarchetypeArtifactId`: The archetype used to create the initial structure of
   the project.
   - `DinteractiveMode`: Create the project using batch mode (optional).

This message indicates that the project was set up successfully:

```shell
...
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  3.429 s
[INFO] Finished at: 2020-01-28T11:47:04Z
[INFO] ------------------------------------------------------------------------
```

In the folder where you ran the command, a new directory should be displayed.
The directory name should match the `DartifactId` parameter, which in this case,
is `my-project`.

## Build a Java project with Gradle

This section explains how to install Gradle and initialize a Java project.

If you already use Gradle and know how to build your own packages, go to the
[next section](#authenticate-to-the-package-registry-with-maven).

### Install Gradle

If you want to create a new Gradle project, you must install Gradle. Follow
instructions at [gradle.org](https://gradle.org/install/) to download and install
Gradle for your local development environment.

In your terminal, verify you can use Gradle by running:

```shell
gradle -version
```

To use an existing Gradle project, in the project directory,
on Linux execute `gradlew`, or on Windows execute `gradlew.bat`.

The output should be similar to:

```plaintext
------------------------------------------------------------
Gradle 6.0.1
------------------------------------------------------------

Build time:   2019-11-18 20:25:01 UTC
Revision:     fad121066a68c4701acd362daf4287a7c309a0f5

Kotlin:       1.3.50
Groovy:       2.5.8
Ant:          Apache Ant(TM) version 1.10.7 compiled on September 1 2019
JVM:          11.0.5 (Oracle Corporation 11.0.5+10)
OS:           Windows 10 10.0 amd64
```

### Create a Java project

Follow these steps to create a Maven project that can be
published to the GitLab Package Registry.

1. Open your terminal and create a directory to store the project.
1. From this new directory, run this Maven command to initialize a new package:

   ```shell
   gradle init
   ```

   The output should be:

   ```plaintext
   Select type of project to generate:
     1: basic
     2: application
     3: library
     4: Gradle plugin
   Enter selection (default: basic) [1..4]
   ```

1. Enter `3` to create a new Library project. The output should be:

   ```plaintext
   Select implementation language:
     1: C++
     2: Groovy
     3: Java
     4: Kotlin
     5: Scala
     6: Swift
   ```

1. Enter `3` to create a new Java Library project. The output should be:

   ```plaintext
   Select build script DSL:
     1: Groovy
     2: Kotlin
   Enter selection (default: Groovy) [1..2]
   ```

1. Enter `1` to create a new Java Library project that is described in Groovy DSL. The output should be:

   ```plaintext
   Select test framework:
     1: JUnit 4
     2: TestNG
     3: Spock
     4: JUnit Jupiter
   ```

1. Enter `1` to initialize the project with JUnit 4 testing libraries. The output should be:

   ```plaintext
   Project name (default: test):
   ```

1. Enter a project name or press Enter to use the directory name as project name.

## Authenticate to the Package Registry with Maven

To authenticate to the Package Registry, you need either a personal access token or deploy token.

- If you use a [personal access token](../../../user/profile/personal_access_tokens.md), set the scope to `api`.
- If you use a [deploy token](../../project/deploy_tokens/index.md), set the scope to `read_package_registry`, `write_package_registry`, or both.

### Authenticate with a personal access token in Maven

To use a personal access token, add this section to your
[`settings.xml`](https://maven.apache.org/settings.html) file.

The `name` must be `Private-Token`.

```xml
<settings>
  <servers>
    <server>
      <id>gitlab-maven</id>
      <configuration>
        <httpHeaders>
          <property>
            <name>Private-Token</name>
            <value>REPLACE_WITH_YOUR_PERSONAL_ACCESS_TOKEN</value>
          </property>
        </httpHeaders>
      </configuration>
    </server>
  </servers>
</settings>
```

### Authenticate with a deploy token in Maven

> - [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/213566) deploy token authentication in [GitLab Premium](https://about.gitlab.com/pricing/) 13.0.
> - [Moved](https://gitlab.com/gitlab-org/gitlab/-/issues/221259) to GitLab Core in 13.3.

To use a deploy token, add this section to your
[`settings.xml`](https://maven.apache.org/settings.html) file.

The `name` must be `Deploy-Token`.

```xml
<settings>
  <servers>
    <server>
      <id>gitlab-maven</id>
      <configuration>
        <httpHeaders>
          <property>
            <name>Deploy-Token</name>
            <value>REPLACE_WITH_YOUR_DEPLOY_TOKEN</value>
          </property>
        </httpHeaders>
      </configuration>
    </server>
  </servers>
</settings>
```

### Authenticate with a CI job token in Maven

To authenticate with a CI job token, add this section to your
[`settings.xml`](https://maven.apache.org/settings.html) file.

The `name` must be `Job-Token`.

```xml
<settings>
  <servers>
    <server>
      <id>gitlab-maven</id>
      <configuration>
        <httpHeaders>
          <property>
            <name>Job-Token</name>
            <value>${env.CI_JOB_TOKEN}</value>
          </property>
        </httpHeaders>
      </configuration>
    </server>
  </servers>
</settings>
```

Read more about [how to create Maven packages using GitLab CI/CD](#create-maven-packages-with-gitlab-cicd).

## Authenticate to the Package Registry with Gradle

To authenticate to the Package Registry, you need either a personal access token or deploy token.

- If you use a [personal access token](../../../user/profile/personal_access_tokens.md), set the scope to `api`.
- If you use a [deploy token](../../project/deploy_tokens/index.md), set the scope to `read_package_registry`, `write_package_registry`, or both.

### Authenticate with a personal access token in Gradle

Create a file `~/.gradle/gradle.properties` with the following content:

```groovy
gitLabPrivateToken=REPLACE_WITH_YOUR_PERSONAL_ACCESS_TOKEN
```

Add a `repositories` section to your
[`build.gradle`](https://docs.gradle.org/current/userguide/tutorial_using_tasks.html)
file:

```groovy
repositories {
    maven {
        url "https://gitlab.example.com/api/v4/groups/<group>/-/packages/maven"
        name "GitLab"
        credentials(HttpHeaderCredentials) {
            name = 'Private-Token'
            value = gitLabPrivateToken
        }
        authentication {
            header(HttpHeaderAuthentication)
        }
    }
}
```

### Authenticate with a deploy token in Gradle

To authenticate with a deploy token, add a `repositories` section to your
[`build.gradle`](https://docs.gradle.org/current/userguide/tutorial_using_tasks.html)
file:

```groovy
repositories {
    maven {
        url "https://gitlab.example.com/api/v4/groups/<group>/-/packages/maven"
        name "GitLab"
        credentials(HttpHeaderCredentials) {
            name = 'Deploy-Token'
            value = '<deploy-token>'
        }
        authentication {
            header(HttpHeaderAuthentication)
        }
    }
}
```

### Authenticate with a CI job token in Gradle

To authenticate with a CI job token, add a `repositories` section to your
[`build.gradle`](https://docs.gradle.org/current/userguide/tutorial_using_tasks.html)
file:

```groovy
repositories {
    maven {
        url "https://gitlab.example.com/api/v4/groups/<group>/-/packages/maven"
        name "GitLab"
        credentials(HttpHeaderCredentials) {
            name = 'Job-Token'
            value = System.getenv("CI_JOB_TOKEN")
        }
        authentication {
            header(HttpHeaderAuthentication)
        }
    }
}
```

## Use the GitLab endpoint for Maven packages

To use the GitLab endpoint for Maven packages, choose an option:

- **Project-level**: Use when you have few Maven packages and they are not in
  the same GitLab group.
- **Group-level**: Use when you have many Maven packages in the same GitLab
  group.
- **Instance-level**: Use when you have many Maven packages in different
  GitLab groups or in their own namespace.

The option you choose determines the settings you add to your `pom.xml` file.

In all cases, to publish a package, you need:

- A project-specific URL in the `distributionManagement` section.
- A `repository` and `distributionManagement` section.

### Project-level Maven endpoint

The relevant `repository` section of your `pom.xml`
in Maven should look like this:

```xml
<repositories>
  <repository>
    <id>gitlab-maven</id>
    <url>https://gitlab.example.com/api/v4/projects/PROJECT_ID/packages/maven</url>
  </repository>
</repositories>
<distributionManagement>
  <repository>
    <id>gitlab-maven</id>
    <url>https://gitlab.example.com/api/v4/projects/PROJECT_ID/packages/maven</url>
  </repository>
  <snapshotRepository>
    <id>gitlab-maven</id>
    <url>https://gitlab.example.com/api/v4/projects/PROJECT_ID/packages/maven</url>
  </snapshotRepository>
</distributionManagement>
```

The corresponding section in Gradle would be:

```groovy
repositories {
    maven {
        url "https://gitlab.example.com/api/v4/projects/PROJECT_ID/packages/maven"
        name "GitLab"
    }
}
```

- The `id` is what you [defined in `settings.xml`](#authenticate-to-the-package-registry-with-maven).
- The `PROJECT_ID` is your project ID, which you can view on your project's home page.
- Replace `gitlab.example.com` with your domain name.
- For retrieving artifacts, use either the
  [URL-encoded](../../../api/README.md#namespaced-path-encoding) path of the project
  (like `group%2Fproject`) or the project's ID (like `42`). However, only the
  project's ID can be used for publishing.

### Group-level Maven endpoint

> - [Introduced](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/8798) in [GitLab Premium](https://about.gitlab.com/pricing/) 11.7.
> - [Moved](https://gitlab.com/gitlab-org/gitlab/-/issues/221259) to GitLab Core in 13.3.

If you rely on many packages, it might be inefficient to include the `repository` section
with a unique URL for each package. Instead, you can use the group-level endpoint for
all the Maven packages stored within one GitLab group. Only packages you have access to
are available for download.

The group-level endpoint works with any package names, so you
have more flexibility in naming, compared to the [instance-level endpoint](#instance-level-maven-endpoint).
However, GitLab does not guarantee the uniqueness of package names within
the group. You can have two projects with the same package name and package
version. As a result, GitLab serves whichever one is more recent.

This example shows the relevant `repository` section of your `pom.xml` file.
You still need a project-specific URL for publishing a package in
the `distributionManagement` section:

```xml
<repositories>
  <repository>
    <id>gitlab-maven</id>
    <url>https://gitlab.example.com/api/v4/groups/GROUP_ID/-/packages/maven</url>
  </repository>
</repositories>
<distributionManagement>
  <repository>
    <id>gitlab-maven</id>
    <url>https://gitlab.example.com/api/v4/projects/PROJECT_ID/packages/maven</url>
  </repository>
  <snapshotRepository>
    <id>gitlab-maven</id>
    <url>https://gitlab.example.com/api/v4/projects/PROJECT_ID/packages/maven</url>
  </snapshotRepository>
</distributionManagement>
```

For Gradle, the corresponding `repositories` section would look like:

```groovy
repositories {
    maven {
        url "https://gitlab.example.com/api/v4/groups/GROUP_ID/-/packages/maven"
        name "GitLab"
    }
}
```

- For the `id`, use what you [defined in `settings.xml`](#authenticate-to-the-package-registry-with-maven).
- For `my-group`, use your group name.
- For `PROJECT_ID`, use your project ID, which you can view on your project's home page.
- Replace `gitlab.example.com` with your domain name.
- For retrieving artifacts, use either the
  [URL-encoded](../../../api/README.md#namespaced-path-encoding) path of the group
  (like `group%2Fsubgroup`) or the group's ID (like `12`).

### Instance-level Maven endpoint

> - [Introduced](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/8274) in [GitLab Premium](https://about.gitlab.com/pricing/) 11.7.
> - [Moved](https://gitlab.com/gitlab-org/gitlab/-/issues/221259) to GitLab Core in 13.3.

If you rely on many packages, it might be inefficient to include the `repository` section
with a unique URL for each package. Instead, you can use the instance-level endpoint for
all Maven packages stored in GitLab. All packages you have access to are available
for download.

**Only packages that have the same path as the project** are exposed by
the instance-level endpoint.

| Project | Package | Instance-level endpoint available |
| ------- | ------- | --------------------------------- |
| `foo/bar`           | `foo/bar/1.0-SNAPSHOT`           | Yes |
| `gitlab-org/gitlab` | `foo/bar/1.0-SNAPSHOT`           | No  |
| `gitlab-org/gitlab` | `gitlab-org/gitlab/1.0-SNAPSHOT` | Yes |

This example shows how relevant `repository` section of your `pom.xml`.
You still need a project-specific URL in the `distributionManagement` section.

```xml
<repositories>
  <repository>
    <id>gitlab-maven</id>
    <url>https://gitlab.example.com/api/v4/packages/maven</url>
  </repository>
</repositories>
<distributionManagement>
  <repository>
    <id>gitlab-maven</id>
    <url>https://gitlab.example.com/api/v4/projects/PROJECT_ID/packages/maven</url>
  </repository>
  <snapshotRepository>
    <id>gitlab-maven</id>
    <url>https://gitlab.example.com/api/v4/projects/PROJECT_ID/packages/maven</url>
  </snapshotRepository>
</distributionManagement>
```

The corresponding repositories section in Gradle would look like:

```groovy
repositories {
    maven {
        url "https://gitlab.example.com/api/v4/packages/maven"
        name "GitLab"
    }
}
```

- The `id` is what you [defined in `settings.xml`](#authenticate-to-the-package-registry-with-maven).
- The `PROJECT_ID` is your project ID, which you can view on your project's home page.
- Replace `gitlab.example.com` with your domain name.
- For retrieving artifacts, use either the
  [URL-encoded](../../../api/README.md#namespaced-path-encoding) path of the project
  (like `group%2Fproject`) or the project's ID (like `42`). However, only the
  project's ID can be used for publishing.

## Publish a package

After you have set up the [remote and authentication](#authenticate-to-the-package-registry-with-maven)
and [configured your project](#use-the-gitlab-endpoint-for-maven-packages),
publish a Maven artifact from your project.

### Publish by using Maven

To publish a package by using Maven:

```shell
mvn deploy
```

If the deploy is successful, the build success message should be displayed:

```shell
...
[INFO] BUILD SUCCESS
...
```

The message should also show that the package was published to the correct location:

```shell
Uploading to gitlab-maven: https://gitlab.example.com/api/v4/projects/PROJECT_ID/packages/maven/com/mycompany/mydepartment/my-project/1.0-SNAPSHOT/my-project-1.0-20200128.120857-1.jar
```

### Publish by using Gradle

To publish a package by using Gradle:

1. Add the Gradle plugin [`maven-publish`](https://docs.gradle.org/current/userguide/publishing_maven.html) to the plugins section:

   ```groovy
   plugins {
       id 'java'
       id 'maven-publish'
   }
   ```

1. Add a `publishing` section:

   ```groovy
   publishing {
       publications {
           library(MavenPublication) {
               from components.java
           }
       }
       repositories {
           maven {
               url "https://gitlab.example.com/api/v4/projects/<PROJECT_ID>/packages/maven"
               credentials(HttpHeaderCredentials) {
                   name = "Private-Token"
                   value = gitLabPrivateToken // the variable resides in ~/.gradle/gradle.properties
               }
               authentication {
                   header(HttpHeaderAuthentication)
               }
           }
       }
   }
   ```

1. Replace `PROJECT_ID` with your project ID, which can be found on your project's home page.

1. Run the publish task:

   ```shell
   gradle publish
   ```

Now navigate to your project's **Packages & Registries** page and view the published artifacts.

## Install a package

To install a package from the GitLab Package Registry, you must configure
the [remote and authenticate](#authenticate-to-the-package-registry-with-maven).
When this is completed, there are two ways to install a package.

### Use Maven with `mvn install`

To install a package by using `mvn install`:

1. Add the dependency manually to your project `pom.xml` file.
   To add the example created earlier, the XML would be:

   ```xml
   <dependency>
     <groupId>com.mycompany.mydepartment</groupId>
     <artifactId>my-project</artifactId>
     <version>1.0-SNAPSHOT</version>
   </dependency>
   ```

1. In your project, run the following:

   ```shell
   mvn install
   ```

The message should show that the package is downloading from the Package Registry:

```shell
Downloading from gitlab-maven: http://gitlab.example.com/api/v4/projects/PROJECT_ID/packages/maven/com/mycompany/mydepartment/my-project/1.0-SNAPSHOT/my-project-1.0-20200128.120857-1.pom
```

### Use Maven with `mvn dependency:get`

You can install packages by using the Maven commands directly.

1. In your project directory, run:

   ```shell
   mvn dependency:get -Dartifact=com.nickkipling.app:nick-test-app:1.1-SNAPSHOT
   ```

The message should show that the package is downloading from the Package Registry:

```shell
Downloading from gitlab-maven: http://gitlab.example.com/api/v4/projects/PROJECT_ID/packages/maven/com/mycompany/mydepartment/my-project/1.0-SNAPSHOT/my-project-1.0-20200128.120857-1.pom
```

NOTE:
In the GitLab UI, on the Package Registry page for Maven, you can view and copy these commands.

### Use Gradle

Add a [dependency](https://docs.gradle.org/current/userguide/declaring_dependencies.html) to `build.gradle` in the dependencies section:

```groovy
dependencies {
    implementation 'com.mycompany.mydepartment:my-project:1.0-SNAPSHOT'
}
```

## Remove a package

For your project, go to **Packages & Registries > Package Registry**.

To remove a package, click the red trash icon or, from the package details, the **Delete** button.

## Create Maven packages with GitLab CI/CD

After you have configured your repository to use the Package Repository for Maven,
you can configure GitLab CI/CD to build new packages automatically.

### Create Maven packages with GitLab CI/CD by using Maven

You can create a new package each time the `master` branch is updated.

1. Create a `ci_settings.xml` file that serves as Maven's `settings.xml` file.

1. Add the `server` section with the same ID you defined in your `pom.xml` file.
   For example, use `gitlab-maven` as the ID:

   ```xml
   <settings xmlns="http://maven.apache.org/SETTINGS/1.1.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:schemaLocation="http://maven.apache.org/SETTINGS/1.1.0 http://maven.apache.org/xsd/settings-1.1.0.xsd">
     <servers>
       <server>
         <id>gitlab-maven</id>
         <configuration>
           <httpHeaders>
             <property>
               <name>Job-Token</name>
               <value>${env.CI_JOB_TOKEN}</value>
             </property>
           </httpHeaders>
         </configuration>
       </server>
     </servers>
   </settings>
   ```

1. Make sure your `pom.xml` file includes the following.
   You can either let Maven use the CI environment variables, as shown in this example,
   or you can hard code your server's hostname and project's ID.

   ```xml
   <repositories>
     <repository>
       <id>gitlab-maven</id>
       <url>${env.CI_SERVER_URL}/api/v4/projects/${env.CI_PROJECT_ID}/packages/maven</url>
     </repository>
   </repositories>
   <distributionManagement>
     <repository>
       <id>gitlab-maven</id>
       <url>${env.CI_SERVER_URL}/api/v4/projects/${env.CI_PROJECT_ID}/packages/maven</url>
     </repository>
     <snapshotRepository>
       <id>gitlab-maven</id>
       <url>${env.CI_SERVER_URL}/api/v4/projects/${env.CI_PROJECT_ID}/packages/maven</url>
     </snapshotRepository>
   </distributionManagement>
   ```

1. Add a `deploy` job to your `.gitlab-ci.yml` file:

   ```yaml
   deploy:
     image: maven:3.6-jdk-11
     script:
       - 'mvn deploy -s ci_settings.xml'
     only:
       - master
   ```

1. Push those files to your repository.

The next time the `deploy` job runs, it copies `ci_settings.xml` to the
user's home location. In this example:

- The user is `root`, because the job runs in a Docker container.
- Maven uses the configured CI [environment variables](../../../ci/variables/README.md#predefined-environment-variables).

### Create Maven packages with GitLab CI/CD by using Gradle

You can create a package each time the `master` branch
is updated.

1. Authenticate with [a CI job token in Gradle](#authenticate-with-a-ci-job-token-in-gradle).

1. Add a `deploy` job to your `.gitlab-ci.yml` file:

   ```yaml
   deploy:
     image: gradle:6.5-jdk11
     script:
       - 'gradle publish'
     only:
       - master
   ```

1. Commit files to your repository.

When the pipeline is successful, the package is created.

### Version validation

The version string is validated by using the following regex.

```ruby
\A(\.?[\w\+-]+\.?)+\z
```

You can play around with the regex and try your version strings on [this regular expression editor](https://rubular.com/r/rrLQqUXjfKEoL6).

## Troubleshooting

### Review network trace logs

If you are having issues with the Maven Repository, you may want to review network trace logs.

For example, try to run `mvn deploy` locally with a PAT token and use these options:

```shell
mvn deploy \
-Dorg.slf4j.simpleLogger.log.org.apache.maven.wagon.providers.http.httpclient=trace \
-Dorg.slf4j.simpleLogger.log.org.apache.maven.wagon.providers.http.httpclient.wire=trace
```

WARNING:
When you set these options, all network requests are logged and a large amount of output is generated.

### Useful Maven command-line options

There are some [Maven command-line options](https://maven.apache.org/ref/current/maven-embedder/cli.html)
that you can use when performing tasks with GitLab CI/CD.

- File transfer progress can make the CI logs hard to read.
  Option `-ntp,--no-transfer-progress` was added in
  [3.6.1](https://maven.apache.org/docs/3.6.1/release-notes.html#User_visible_Changes).
  Alternatively, look at `-B,--batch-mode`
  [or lower level logging changes.](https://stackoverflow.com/questions/21638697/disable-maven-download-progress-indication)

- Specify where to find the `pom.xml` file (`-f,--file`):

   ```yaml
   package:
     script:
       - 'mvn --no-transfer-progress -f helloworld/pom.xml package'
   ```

- Specify where to find the user settings (`-s,--settings`) instead of
  [the default location](https://maven.apache.org/settings.html). There's also a `-gs,--global-settings` option:

   ```yaml
   package:
     script:
       - 'mvn -s settings/ci.xml package'
   ```

### Verify your Maven settings

If you encounter issues within CI/CD that relate to the `settings.xml` file, try adding
an additional script task or job to [verify the effective settings](https://maven.apache.org/plugins/maven-help-plugin/effective-settings-mojo.html).

The help plugin can also provide
[system properties](https://maven.apache.org/plugins/maven-help-plugin/system-mojo.html), including environment variables:

```yaml
mvn-settings:
  script:
    - 'mvn help:effective-settings'

package:
  script:
    - 'mvn help:system'
    - 'mvn package'
```