title: Specify default value for a logback property, in spring-boot
body: <p>In <code>spring-boot</code> application, I am trying to config a default dir for <code>logback</code>.</p>
  
  <p>Usually, in <code>logback.xml</code> I would config it this way:</p>
  
  <pre><code>&lt;property name="logFile.dir" value="${catalina.home:-/tmp}/logs" /&gt;
  </code></pre>
  
  <p>The separator is <code>:-</code>.</p>
  
  <p>But, in <code>application.properties</code>:</p>
  
  <p>I have to config it this way:</p>
  
  <pre><code>logging.file=${catalina.home:/tmp}/logs/sportslight.log
  </code></pre>
  
  <p>Need to change the separator from <code>:-</code> to <code>:</code>.</p>
  
  <p>The questions are:</p>
  
  <ul>
  <li>In <code>logback.xml</code>, which is the correct separator, <code>:-</code> or <code>:</code>?</li>
  <li>In <code>application.properties</code>, why only <code>:</code> works, is it because spring-boot would handle it first before pass the value to logback? </li>
  </ul>