title: How to identify and set a missing environment property in Maven?
body: <p>I have my build set-up so that I pass in my variable via the command line:</p>
  
  <pre><code>mvn clean install -DsomeVariable=data
  </code></pre>
  
  <p>In my pom I have:</p>
  
  <pre><code>&lt;someTag&gt;${someVariable}&lt;/someTag&gt;
  </code></pre>
  
  <p>This works fine, but I would like to identify if someVariable is not specified on the command line, and then default it so that my script can continue.</p>
  
  <p>Can this be done in Maven?</p>