title: What is the meaning of `X{code}` in Drop-wizard log format
body: <p>Sorry if I am asking very basic question here. But i am using a dropwizard application in which log format is given as <code>"%-6level [%d{HH:mm:ss.SSS}] [%t] %logger{5} - %X{code} %msg %n"</code>. </p>
  
  <p>And application logs contains below lines :-</p>
  
  <pre><code>INFO  [2017-06-07 13:54:43,828] com.foo.Bar: In Get Method
  </code></pre>
  
  <p>I understood that meaning of <code>%-6level , date and %t and %msg %n</code> in log format but couldn't get the meaning of <strong>%X{code}</strong> and <strong>%logger{5}</strong> and don't see these printing in my logs.</p>
  
  <p>Can someone point me to a proper doc where each of these parameters of log format is explained in details.</p>