title: POJOs as documents in mongodb
body: <p>I am trying to save entity as documents in Mongodb and tried to create Codec for it . And it does not seem to work . I tried Morphia but, i am not able to find documentation on adding extra fields into document at runtime using morphia. this would defy the basic purpose of using Mongodb at first place . 
  I initially want my documents to have fixed number of fields that are in POJO . and during the run of application the number of fields should change </p>
  
  <p>Can any one suggest me what should i do </p>