title: Jackson - Transform field value on serialization
body: <p>In a Spring Boot applicaion with AngularJS frontend, a "Pin" field value has to be blackened on serialization, i.e., if the Pin field value is null in the POJO, the according JSON field has to remain blank; if the field value contains data, it has to be replaced with a "***" string.</p>
  
  <p>Does Jackson provide a feature to get this done?</p>