title: is_undefined directory error in logack with Spring Boot application
body: <p>I am getting log.dir_IS_UNDEFINED error even though I'm passing log.dir as a java parameter -Dlog.dir="/logs"</p>
  
  <p>Here is a snippet of my logback.xml file</p>
  
  <pre><code>&lt;appender name="FILE" class="ch.qos.logback.core.rolling.RollingFileAppender"&gt;
          &lt;file&gt;${log.dir}/crm.log&lt;/file&gt;
          &lt;rollingPolicy class="ch.qos.logback.core.rolling.TimeBasedRollingPolicy"&gt;
  </code></pre>