title: How can @QueryParam translate a parameter without value to boolean "false"?
body: <p>I'd like to use an URL like <code>http://www.example.com/rest/foo?bar</code> where the <code>bar</code> query parameter has no value and its presence alone should denote if a variable is <code>true</code> or <code>false</code>.  </p>
  
  <p>Currently the missing value is assumed to be <code>""</code> (empty) and passed to <code>new Boolean()</code> which treats it as <code>false</code>.  </p>
  
  <p>Is there a more elegant way of defining it than declaring the parameter to be String and converting it myself?  </p>
  
  <p>Like e.g. a class <code>javax.rs.BooleanFlag</code> or similar?</p>