What does "http://central" mean in my Maven settings.xml?

Question

I've been copying "sample" settings.xml files for ages now, and almost all of them seem to include a repository with the URL http://central. This bugs me, because of course there could actually be a machine on the local domain called "central", so this is a valid URN, but it also must (might?) have some special meaning to Maven.

Is it just shorthand that's commonly used, but the actual URL is ignored? Could I replace it with something else, or remove it entirely? Is it documented anywhere?

If it matters, I develop on a corporate network that has an internal iBiblio mirror, that acts as "central" for us.

Answer 1

AFAIK, it is a bogus URL which mentions at Configure Maven to Download from Nexus as the following example: -

<settings>
  <mirrors>
    <mirror>
      <!--This sends everything else to /public -->
      <id>nexus</id>
      <mirrorOf>*</mirrorOf>
      <url>http://localhost:8081/nexus/content/groups/public</url>
    </mirror>
  </mirrors>
  <profiles>
    <profile>
      <id>nexus</id>
      <!--Enable snapshots for the built in central repo to direct -->
      <!--all requests to nexus via the mirror -->
      <repositories>
        <repository>
          <id>central</id>
          <url>http://central</url>
          <releases><enabled>true</enabled></releases>
          <snapshots><enabled>true</enabled></snapshots>
        </repository>
      </repositories>
     <pluginRepositories>
        <pluginRepository>
          <id>central</id>
          <url>http://central</url>
          <releases><enabled>true</enabled></releases>
          <snapshots><enabled>true</enabled></snapshots>
        </pluginRepository>
      </pluginRepositories>
    </profile>
  </profiles>
  <activeProfiles>
    <!--make the profile active all the time -->
    <activeProfile>nexus</activeProfile>
  </activeProfiles>
</settings>

The nexus profile is configured to download from the central repository with a bogus URL of http://central.

This URL is overridden by the mirror setting in the same settings.xml file to point to the URL of your single Nexus group. The nexus group is then listed as an active profile in the activeProfiles element.

I hope this may help.

Answer 2

We also used exactly this sample config, even with the same comments for about 15(!) years without any problems. For maven builds it does not matter, as always nexus is requested for any dependencies.

But today I tried to built a project with a combined ant+maven build which failed to get dependencies via artifact:remoteRepository Task from central Repo.

The solution was to fix the "url" tag in the central repo: https://repo.maven.apache.org/maven2

So it looks like it doesn't matter in most cases, but to avoid any corner cases, always use the right url.