title: logback-classic does not log Java Exceptions
body: <p>I can confirm that my <code>logback.xml</code> file (placed in <code>src/main/resources</code>) is correctly picked up, and used by the Java executable. I configured it to log everything at <code>INFO</code> level or higher to a <code>FILE</code> and to <code>STDOUT</code>. Everything works as expected (logging is output to both places), except that Exceptions are <em>only</em> logged to <code>STDOUT</code>, but not to the <code>FILE</code>. What's missing in my <code>logback.xml</code>?</p>
  
  <pre><code>&lt;configuration&gt;
      &lt;appender name="FILE" class="ch.qos.logback.core.FileAppender"&gt;
          &lt;file&gt;./logs/batch.log&lt;/file&gt;
          &lt;append&gt;true&lt;/append&gt;
          &lt;encoder&gt;
              &lt;pattern&gt;%date [%level] from %logger - %message%n%xException&lt;/pattern&gt;
          &lt;/encoder&gt;
      &lt;/appender&gt;
  
      &lt;appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender"&gt;
          &lt;encoder&gt;
              &lt;pattern&gt;%date [%level] from %logger - %message%n%xException&lt;/pattern&gt;
          &lt;/encoder&gt;
      &lt;/appender&gt;
  
      &lt;root level="INFO"&gt;
          &lt;appender-ref ref="STDOUT"/&gt;
          &lt;appender-ref ref="FILE"/&gt;
      &lt;/root&gt;
  &lt;/configuration&gt;
  </code></pre>