title: maven repository setting.xml the mirrorof
body: <pre class="lang-xml prettyprint-override"><code>&lt;mirrors&gt;
      &lt;!-- mirror
       | Specifies a repository mirror site to use instead of a given repository. The repository that
       | this mirror serves has an ID that matches the mirrorOf element of this mirror. IDs are used
       | for inheritance and direct lookup purposes, and must be unique across the set of mirrors.
       |
      &lt;mirror&gt;
        &lt;id&gt;mirrorId&lt;/id&gt;
        &lt;mirrorOf&gt;repositoryId&lt;/mirrorOf&gt;
        &lt;name&gt;Human Readable Name for this Mirror.&lt;/name&gt;
        &lt;url&gt;http://my.repository.com/repo/path&lt;/url&gt;
      &lt;/mirror&gt;
       --&gt;
      &lt;mirror&gt;
          &lt;id&gt;nexus-osc&lt;/id&gt;
          &lt;mirrorOf&gt;central&lt;/mirrorOf&gt;
          &lt;name&gt;Nexus osc&lt;/name&gt;
          &lt;url&gt;http://maven.oschina.net/content/groups/public/&lt;/url&gt;
      &lt;/mirror&gt;
      &lt;mirror&gt;
          &lt;id&gt;nexus-osc-thirdparty&lt;/id&gt;
          &lt;mirrorOf&gt;thirdparty&lt;/mirrorOf&gt;
          &lt;name&gt;Nexus osc thirdparty&lt;/name&gt;
          &lt;url&gt;http://maven.oschina.net/content/repositories/thirdparty/&lt;/url&gt;
      &lt;/mirror&gt;
      &lt;mirror&gt;
          &lt;id&gt;maven2&lt;/id&gt;
          &lt;mirrorOf&gt;maven2&lt;/mirrorOf&gt;
          &lt;name&gt;maven2&lt;/name&gt;
          &lt;url&gt;http://repo1.maven.org/maven2/&lt;/url&gt;
      &lt;/mirror&gt;
  &lt;/mirrors&gt;
  </code></pre>
  
  <p>What is the exactly using of <code>mirrorOf</code>? Will maven first try get jar from <code>id=nexus-osc</code> and then <code>nexus-osc-thirdparty</code> and then <code>maven2</code>?
  I have already checked the <a href="https://maven.apache.org/guides/mini/guide-mirror-settings.html" rel="noreferrer">maven mirror setting guide</a> but I still can not understand.</p>