title: MappingJackson2HttpMessageConverter & Serialization
body: <p>Based on the below guide
  <a href="https://spring.io/guides/gs/rest-service/" rel="nofollow">https://spring.io/guides/gs/rest-service/</a></p>
  
  <p>MappingJackson2HttpMessageConverter converts the Greeting Object to JSON. Question is, why isn't Greeting Object implementing Serializable? Is it a miss in the guide or not required?</p>