• Publish to the GitLab Package Registry
  • Authenticate to the Package Registry
  • Edit the settings.xml
  • Naming convention
    • Endpoint URLs
  • Edit the pom.xml for publishing
• Publish a package
• Install a package
  • Use Maven with mvn install
  • Use Maven with mvn dependency:get
• Helpful hints
  • Publishing a package with the same name or version
  • Do not allow duplicate Maven packages
  • Request forwarding to Maven Central
    • Setting GitLab as a mirror for the central proxy
  • Create Maven packages with GitLab CI/CD
  • Create Maven packages with GitLab CI/CD using Maven
  • Version validation
  • Useful Maven command-line options
  • Supported CLI commands
• Troubleshooting
  • Review network trace logs
  • Verify your Maven settings

Maven packages in the Package Registry

Publish Maven artifacts in your project’s Package Registry. Then, install the packages whenever you need to use them as a dependency.

For documentation of the specific API endpoints that the Maven package manager client uses, see the Maven API documentation.

Learn how to build a Maven package.

Publish to the GitLab Package Registry

Authenticate to the Package Registry

You need an token to publish a package. There are different tokens available depending on what you’re trying to achieve. For more information, review the guidance on tokens.

Create a token and save it to use later in the process.

Do not use authentication methods other than the methods documented here. Undocumented authentication methods might be removed in the future.

Edit the settings.xml

Add the following section to your settings.xml file.

<settings>
  <servers>
    <server>
      <id>gitlab-maven</id>
      <configuration>
        <httpHeaders>
          <property>
            <name>REPLACE_WITH_NAME</name>
            <value>REPLACE_WITH_TOKEN</value>
          </property>
        </httpHeaders>
      </configuration>
    </server>
  </servers>
</settings>

Naming convention

You can use one of three endpoints to install a Maven package. You must publish a package to a project, but the endpoint you choose determines the settings you add to your pom.xml file for publishing.

The three endpoints are:

• Project-level: Use when you have a few Maven packages and they are not in the same GitLab group.
• Group-level: Use when you want to install packages from many different projects in the same GitLab group. 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.
• Instance-level: Use when you have many packages in different GitLab groups or in their own namespace.

For the instance-level endpoint, ensure the relevant section of your pom.xml in Maven looks like this:

  <groupId>group-slug.subgroup-slug</groupId>
  <artifactId>project-slug</artifactId>

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

Endpoint URLs

Edit the pom.xml for publishing

No matter which endpoint you choose, you must have:

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

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

<repositories>
  <repository>
    <id>gitlab-maven</id>
    <url><your_endpoint_url></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 id is what you defined in settings.xml.
• The <your_endpoint_url> depends on which endpoint you choose.
• Replace gitlab.example.com with your domain name.

Publish a package

After you have set up the authentication and chosen an endpoint for publishing, publish a Maven package to your project.

To publish a package by using Maven:

mvn deploy

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

...
[INFO] BUILD SUCCESS
...

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

Uploading to gitlab-maven: https://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

Install a package

To install a package from the GitLab Package Registry, you must configure the remote and authenticate. When this is completed, you can install a package from a project, group, or namespace.

If multiple packages have the same name and version, when you install a package, the most recently-published package is retrieved.

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:

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

2. In your project, run the following:

   mvn install
   

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

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 dependency:get command directly.

1. In your project directory, run:

   mvn dependency:get -Dartifact=com.nickkipling.app:nick-test-app:1.1-SNAPSHOT -DremoteRepositories=gitlab-maven::::<gitlab endpoint url>  -s <path to settings.xml>
   

   • <gitlab endpoint url> is the URL of the GitLab endpoint.
   • <path to settings.xml> is the path to the settings.xml file that contains the authentication details.

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

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

Helpful hints

Publishing a package with the same name or version

When you publish a package with the same name and version as an existing package, the new package files are added to the existing package. You can still use the UI or API to access and view the existing package’s older assets.

To delete older package versions, consider using the Packages API or the UI.

Do not allow duplicate Maven packages

To prevent users from publishing duplicate Maven packages, you can use the GraphQl API or the UI.

In the UI:

1. For your group, go to Settings > Packages and registries.
2. Expand the Package Registry section.
3. Turn on the Do not allow duplicates toggle.
4. Optional. To allow some duplicate packages, in the Exceptions box, enter a regex pattern that matches the names and/or versions of packages you want to allow.

Your changes are automatically saved.

Request forwarding to Maven Central

When a Maven package is not found in the Package Registry, the request is forwarded to Maven Central.

When the feature flag is enabled, administrators can disable this behavior in the Continuous Integration settings.

There are many ways to configure your Maven project so that it requests packages in Maven Central from GitLab. Maven repositories are queried in a specific order. By default, maven-central is usually checked first through the Super POM, so GitLab needs to be configured to be queried before maven-central.

Using GitLab as a mirror of the central proxy is one way to force GitLab to be queried in place of maven-central.

Maven forwarding is restricted to only the project level and group level endpoints. The instance level endpoint has naming restrictions that prevent it from being used for packages that don’t follow that convention and also introduces too much security risk for supply-chain style attacks.

Setting GitLab as a mirror for the central proxy

To ensure all package requests are sent to GitLab instead of Maven Central, you can override Maven Central as the central repository by adding a <mirror> section to your settings.xml:

<settings>
  <servers>
    <server>
      <id>central-proxy</id>
      <configuration>
        <httpHeaders>
          <property>
            <name>Private-Token</name>
            <value><personal_access_token></value>
          </property>
        </httpHeaders>
      </configuration>
    </server>
  </servers>
  <mirrors>
    <mirror>
      <id>central-proxy</id>
      <name>GitLab proxy of central repo</name>
      <url>https://gitlab.example.com/api/v4/projects/<project_id>/packages/maven</url>
      <mirrorOf>central</mirrorOf>
    </mirror>
  </mirrors>
</settings>

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 using Maven

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

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

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

   <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>${CI_JOB_TOKEN}</value>
             </property>
           </httpHeaders>
         </configuration>
       </server>
     </servers>
   </settings>
   

3. Make sure your pom.xml file includes the following. You can either let Maven use the predefined CI/CD variables, as shown in this example, or you can hard code your server’s hostname and project’s ID.

   <repositories>
     <repository>
       <id>gitlab-maven</id>
       <url>${CI_API_V4_URL}/projects/${CI_PROJECT_ID}/packages/maven</url>
     </repository>
   </repositories>
   <distributionManagement>
     <repository>
       <id>gitlab-maven</id>
       <url>${CI_API_V4_URL}/projects/${CI_PROJECT_ID}/packages/maven</url>
     </repository>
     <snapshotRepository>
       <id>gitlab-maven</id>
       <url>${CI_API_V4_URL}/projects/${CI_PROJECT_ID}/packages/maven</url>
     </snapshotRepository>
   </distributionManagement>
   

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

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

5. 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/CD variables.

Version validation

The version string is validated by using the following regex.

\A(?!.*\.\.)[\w+.-]+\z

You can experiment with the regex and try your version strings on this regular expression editor.

Useful Maven command-line options

There are some Maven command-line options 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. Alternatively, look at -B,--batch-mode or lower level logging changes.

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

  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. There’s also a -gs,--global-settings option:

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

Supported CLI commands

The GitLab Maven repository supports the following Maven CLI commands:

• mvn deploy: Publish your package to the Package Registry.
• mvn install: Install packages specified in your Maven project.
• mvn dependency:get: Install a specific package.

Troubleshooting

To improve performance, Maven caches files related to a package. If you encounter issues, clear the cache with these commands:

rm -rf ~/.m2/repository

If you’re using Gradle, run this command to clear the cache:

rm -rf ~/.gradle/caches # Or replace ~/.gradle with your custom GRADLE_USER_HOME

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:

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

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.

The help plugin can also provide system properties, including environment variables:

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

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