How to setup a local Maven repository server for artifact hosting

1.1 Background knowledge

It is assumed that the reader is familiar with the following concepts and technologies:

• Maven. Here is a tutorial on how to install Maven and use it on the command line for those who are unfamiliar
• The enterprise software deployment model for Java EE apps and microservices (e.g. deploying web applications to Tomcat or embedding Spring Boot microservices in an embedded application server)
• Some XML basics

1.2 Purpose of a local Maven repository server

The purpose of a local Maven repository is to serve as an internal private repository of all software libraries used within an organization. Storing Maven artifacts (jars and poms) in a dedicated Maven repository is preferable to storing them in version control systems such as Git or Subversion for the following reasons:

• Libraries (JARS) are binary files and don’t belong in version control systems which are better at handling text files
• Keeps the version control database small
• Checkouts, updates and other actions on the version control system will be quicker

1.3 Advantages of having an internal private local Maven repository

• Reduced likelihood of version conflicts
• Less manual intervention required for doing a build first time
• A single central reference repository of all dependent software libraries rather than several independent local libraries
• It is quicker to do a clean build when using an internal repository as Maven artifacts are retrieved from a server on the intranet rather than the ibiblio server on the internet

1.4 Types of local Maven repository servers

• Local Maven repository – exists on developers machine and is maintained by the developer. It is in sync with the Maven repositories defined in the ‘settings.xml’ in their ‘~home/.m2’ folder. If no private remote internal repository is setup and listed in the pom.xml file or settings.xml file, then this local repository on developers machine is synchronized with the public Maven repo
• Private remote internal Maven repository – This the repository which we will setup. We will change the Maven pom.xml or settings.xml to use this repository
• Public remote external repository – This is the public external repository. By default, Maven synchronizes with this repository.

2. Overview of a local Maven repository server

2.1 Development environment without a local Maven repository server

2.2 Development with an organization wide private Maven repository server

3. Use cases for a local Maven repository server

• Create 2 sub-repositories within the internal repository
• cache for artifacts downloaded and available publicly. This would be synchronized with external repository
• internal-Maven-repository – for organizations internal artifacts. This is not synchronized with any external repository and contains artifacts which are unique to the organization
• Alternatively, another sub-repository can be created for artifacts available publicly but not in the public Maven repo – e.g. later versions of some artifacts. This would not be synchronized with an external repository. We can call this ‘3^rd-party’
• Browse remote repository, preferably using a web browser
• Search for artifacts in the repository
• Download code from version control, change ‘settings.xml’ to point to the internal repository and do a clean build without any manual intervention
• Install new version of an artifact
• Bulk import artifacts into the repository
• Bulk export artifacts from the repository
• Backup the repository manually and setup task to do this automatically

4. Criteria for choosing a local Maven repository server

The ideal Maven repository implementation should be:

• Open source Maven repository server software is preferred
• Provide admin tools
• Provide a Maven repository browser – preferably web browser rather than desktop application.
• Deployed in standard web server – e.g Apache or Tomcat
• Ability to create, edit and delete sub repositories
• Bulk import/export facility to move groups of artifacts into and out of the repository
• Access control facility and anonymous read-only access
• Easy to setup and use
• Backup facility
• Issue tracker, forums and other independent sources of information
• Active community/developers so that the produce is enhanced and bugs fixed

5. Comparison of various Maven repository servers

Some of the popular open source Maven repository servers are:

• Sonatype Nexus
• Standard Maven proxy from codehaus 
• Dead simple Maven Proxy (DSMP) 
• Proximity Maven repository server
• Artifactory 

An Artifactory vs Maven vs Proximity comparison is shown below:

Following review of all products, Artifactory has all the criteria that we are looking for. Proximity Maven repository also seems to have most of the features we are looking for. We will look at implementing the Maven repository using Artifactory.

Other points about JFrog Artifactory are:

• Meets all our requirements
• Apache 2.0 license
• Runs on JDK 1.6 and Tomcat 6. Artifactory is deployed as a ‘war’ file in Tomcat.
• Uses Derby DB to store artefacts. Data is stored in a published and well known format
• All artifacts can be bulk exported to local repository and then imported into some other repository so it is easy to move artifacts from one implementation to another. It also makes upgrades of Maven repository very easy
• Compliant with Java Content Repository standard (JSR-170).
• Uses Lucene as search engine. Repository is indexed and can be re-indexed
• UI done using Ajax
• Easy to customise the UI
• Uses Jira as an issue tracker

6. Setting up the local Maven repository server

Updated open source local Maven repository installation tutorials

The version of Artifactory this tutorial deals with beyond this point in the article is somewhat old. For an updated look at installing either Sonatype Nexus or JFrog Artifactory as your open source local Maven repository of choice, please look at the following two articles, both of which include video tutorials on installation, configuration and JAR file uploads:

• How to setup a JFrog Artifactory private Maven repository
• Getting started with the Sonatype Nexus internal Maven repo

A local Maven repository's friends

6.1 Required Artifactory software

• Artifactory Maven repository (https://jfrog.com/open-source/)
• The latest installation of the JDK

6.2 Artifactory directory structure

Down load and unzip artifactory. The directory structure is shown below:

The folders are:

• Backup – backup of repository. Backup policy can be setup using ‘cron’ expressions. Quartz scheduler is used to run the backup at the specified time. The backup interval is specified in the ‘ARTIFACTORY_INSTALLATION_FOLDER>/etc/artifactory.config.xml’
• Bin – batch files used to run the included jetty web server
• Data – Has derby database files. Everything in this folder can be deleted if you wish to start with a clean repository. In a new installation of artifactory, this folder is empty.
• Etc – Configuration files for artifactory. Has ‘artifactory.config.xml’ and ‘jetty.xml ‘and ‘log4j.,properties’
• Lib – has all the dependent jar files
• Logs – log files
• Webapps – has the ‘war’ file. This can be copied and installed in tomcat.

6.2 Deploy JFrog Artifactory in Tomcat

Deploy the ‘war’ file in ‘<ARTIFACTORY_INSTALLATION_FOLDER>/webapp’ to ‘<TOMCAT_INSTALLATION_FOLDER>/webapps’. No tomcat configuration changes are required with jdk1.6 and Tomcat 6. Tomcat 6 should detect the web application and deploy it.

Once the web applications is deployed, the web application needs this information:

• Location of the database to store the artefacts
• Location of the artifactory config xml file
• Location of backup folder

A single configuration is used to specify all 3. We only have to specify the location of the location of the artifactory installation folder during Tomcat startup and artifactory will be able to work out the rest. An alternative to this approach would have been to setup connection to the derby database using jdbc and to configure artifactory in the web application(by including artifactory.config.xml in the web application). However, this approach is simpler.

The location of artifactory installation folder can be specified as a environment variable. For Linux, use ‘.bash’ script to export the location of the artifactory installation folder as shown below:

export JAVA_OPTS = -Dartifactory.home=/home/amangat/artifactory-1.2.1-rc1

For Windows, it can be added to Tomcat startup options as shown below:

6.3 Setup the snapshot and release Maven repositories

A suggested approach is to create 3 repositories(or sub repositories) in our Maven repository. They are:

• Private-internal-repository: This repository contains artifacts which are used only within the organization. These are manually uploaded by the developer. This does not synchronize with remote repository with ibiblio as the artifacts in this repository(or sub-repository) are private to the organization.
• 3^rd-party: This contains artifacts which are publicly available but not in ibiblio repository. Example could be latest versions of libraries which are not yet available on ibiblio or jdbc drivers. This repository is not synchronized with ibiblio as ibiblio does not have these jars
• Ibiblio-cache: This repository is synchronized with ibiblio repository and is a cache of the artifacts from ibiblio.

This is configured in the <ARTIFACTORY_INSTALLATION_FOLDER>/etc/artifactory.config.xml’. The configuration to setup these 3 repositories is shown below:

<config xmlns:xsi="https://www.w3.org/2001/XMLSchema-instance"
        xmlns="http://artifactory.jfrog.org/xsd/1.0.0"
        xsi:schemaLocation="http://artifactory.jfrog.org/xsd/1.0.0
        http://www.jfrog.org/xsd/artifactory-v1_0_0.xsd">
    <!-- Backup every 12 hours -->
    <!--<backupCronExp>0 0 /12 * * ?</backupCronExp>-->
    <localRepositories>
      <localRepository>
          <key>private-internal-repository</key>
          <description>Private internal repository</description>
          <handleReleases>true</handleReleases>
          <handleSnapshots>true</handleSnapshots>
      </localRepository>
      <localRepository>
          <key>3rd-party</key>
          <description>3rd party jars added manually</description>
          <handleReleases>true</handleReleases>
          <handleSnapshots>false</handleSnapshots>
      </localRepository>
    </localRepositories>
    <remoteRepositories>
      <remoteRepository>
          <key>ibiblio</key>
          <handleReleases>true</handleReleases>
          <handleSnapshots>false</handleSnapshots>
          <excludesPattern>org/artifactory/**,org/jfrog/**</excludesPattern>
          <url>http://repo1.Maven.org/Maven2</url>
      </remoteRepository>
    </remoteRepositories>
</config> 

Start Tomcat and navigate to http://localhost:8080/artifactory. Newer versions run on port 8081.

The artifactory home page is shown below:

Sign in using username ‘admin’ and password ‘password’. Click on the Browse repository link and you should be able to view the contents of the repository.

7. Configuring Maven to use the new local repository server

7.1 Configure Maven using settings.xml

Maven uses the settings.xml file located at ‘~/.m2/settings.xml’ to get the location of Maven repository. If no repository is specified, Maven uses the default repository. The settings.xml file has to be changed to use the new repository. The settings are shown below:

<profiles>
      <profile>
            <id>dev</id>
            <properties>
                  <tomcat5x.home>C:/InstalledPrograms/apache-tomcat-5.5.20</tomcat5x.home>
            </properties>
            <repositories>
                  <repository>
                        <id>central</id>
                        <url>http://localhost:8080/artifactory/repo</url>
                        <snapshots>
                              <enabled>false</enabled>
                        </snapshots>
                  </repository>
                  <repository>
                        <id>snapshots</id>
                        <url>http://localhost:8080/artifactory/repo</url>
                        <releases>
                              <enabled>false</enabled>
                        </releases>
                  </repository>
            </repositories>
            <pluginRepositories>
                  <pluginRepository>
                        <id>central</id>
                        <url>http://localhost:8080/artifactory/repo</url>
                        <snapshots>
                              <enabled>false</enabled>
                        </snapshots>
                  </pluginRepository>
                  <pluginRepository>
                        <id>snapshots</id>
                        <url>http://localhost:8080/artifactory/repo</url>
                        <releases>
                              <enabled>false</enabled>
                        </releases>
                  </pluginRepository>
            </pluginRepositories>
      </profile>
</profiles>

7.2 Configure Maven using project ‘pom.xml’

The repository settings can also be done in the project pom.xml. A simple ‘pom.xml’ is shown below:

<project xmlns="http://Maven.apache.org/POM/4.0.0"
xmlns:xsi="https://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://Maven.apache.org/POM/4.0.0
http://Maven.apache.org/Maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>test</groupId>
<artifactId>test</artifactId>
<packaging>jar</packaging>
<version>1.0-SNAPSHOT</version>
<name>test</name>
<url>http://Maven.apache.org</url>
       <repositories>
                      <repository>
                              <id>central</id>
                      <url>http://localhost:8080/artifactory/repo</url>
                      <snapshots>
                              <enabled>false</enabled>
                      </snapshots>
              </repository>
              <repository>
                      <id>snapshots</id>
                      <url>http://localhost:8080/artifactory/repo</url>
                      <releases>
                              <enabled>false</enabled>
                      </releases>
              </repository>
      </repositories>
      <pluginRepositories>
              <pluginRepository>
                      <id>central</id>
                      <url>http://localhost:8080/artifactory/repo</url>
                      <snapshots>
                              <enabled>false</enabled>
                      </snapshots>
              </pluginRepository>
              <pluginRepository>
                      <id>snapshots</id>
                      <url>http://localhost:8080/artifactory/repo</url>
                      <releases>
                              <enabled>false</enabled>
                      </releases>
              </pluginRepository>
      </pluginRepositories>
<dependencies>
   <dependency>
     <groupId>junit</groupId>
     <artifactId>junit</artifactId>
     <version>3.8.1</version>
     <scope>test</scope>
   </dependency>
</dependencies>
</project>

7.3 How to create a local maven repository server

When building the Maven project, all the repositories should be downloaded using the new repository. The console will show the server Maven uses as shown below:

Login to the new repository using your web browser and you will see that artifactory has downloaded and cached the artifacts from ibiblio.

7.4 Local maven repository server setup complete

Artifacts can be installed using the web UI or using Maven command line. Installation using the web UI is simple and faster and does not require any configuration changes. Installation using the command line requires configuration changes in settings.xml and the it can be used in other scripts.

7.4.1 Installing artifacts using the web UI

The steps involved are shown below:

1. Upload the artifact to deploy (‘jar’ file or ‘pom’ file)

2. Artifactory will create the pom file if you are uploading a jar file. You can also specify which repository to upload to.

3. Once uploaded, the artifact appears in the repository along with the ‘pom’ file created by artifactory.

7.4.1 Installing artifacts from Maven command line

When using ‘mvn clean install’ command, Maven only packages and installs the artifact to the local repository. To install it to the AHP internal repository, we have to add an additional configuration section in the settings.xml. The steps involved are shown below:

<settings>
      <servers>
            <server>
                  <id>organisation-internal</id>
                  <username>admin</username>
                  <password>password</password>
            </server>
      </servers>
</settings>

To install anartifactto internal Maven repository, the command is:

mvn deploy:deploy-file -DrepositoryId=organisation-internal -Durl=http://localhost:8080/artifactory/private-internal-repository
-DgroupId=test -DartifactId=test -Dversion=1.1 -Dpackaging=jar -Dfile=target/test-1.1.jar

The repository id should match the server id defined in the settings.xml. The url should include the name of the repository theartifactis to be installed in.

The new artifact appears in the repository and artifactory has created the ‘pom’ file for us automatically.

8. Other features of Artifactory Maven repository

8.1 How to backup a Maven repository

Backup policy is specified in the <ARTIFACTORY_INSTALLATION_FOLDER>/etc/artifactory.config.xml. Backup schedule is specified using ‘cron’ expression. The backup configuration element is highlighted below:

<config xmlns:xsi="https://www.w3.org/2001/XMLSchema-instance"
        xmlns="http://artifactory.jfrog.org/xsd/1.0.0"
        xsi:schemaLocation="http://artifactory.jfrog.org/xsd/1.0.0
        http://www.jfrog.org/xsd/artifactory-v1_0_0.xsd">
    <!-- Backup every 12 hours -->
    <backupCronExp>0 0 /12 * * ?</backupCronExp>
    <localRepositories>
      <localRepository>
          <key>private-internal-repository</key>
          <description>Private internal repository</description>
          <handleReleases>true</handleReleases>
          <handleSnapshots>true</handleSnapshots>
      </localRepository>
      <localRepository>
          <key>3rd-party</key>
          <description>3rd party jars added manually</description>
          <handleReleases>true</handleReleases>
          <handleSnapshots>false</handleSnapshots>
      </localRepository>
    </localRepositories>
    <remoteRepositories>
      <remoteRepository>
          <key>ibiblio</key>
          <handleReleases>true</handleReleases>
          <handleSnapshots>false</handleSnapshots>
          <excludesPattern>org/artifactory/**,org/jfrog/**</excludesPattern>
          <url>http://repo1.Maven.org/Maven2</url>
      </remoteRepository>
    </remoteRepositories>
</config>

Backups are stored in ‘<ARTIFACTORY_INSTALLATION_FOLDER>/backups’. The backups are in the same format as the local repository on developers machine. This makes it very easy to migrate the repository contents to another implementation of Maven repository.

8.2 Other local Maven repository features

• Delete artifacts using the web UI
• Search for artifacts using the web UI
• Bulk import/export all artifacts in repository
• The included jetty web server can be used if tomcat is not required

9. How to setup a local Maven repository conclusion

An internal private local Maven repository speeds up the build process and makes it easier to do clean builds. It also helps to avoid conflicts due to different versions of libraries.

Amongst the 4 common local Maven repositories available, JFrog Artifactory seems to be the better product.

Artifactory makes it easy to setup a local Maven repository server. It provides all the features which a good Maven repository should implement. The organization will not be locked into this tool as it is easy to migrate the repository contents to another implementation. A web UI makes the repository easy to use even for people who don’t know how the repository works.