anchor.diff:  
   As you can see, Forge has a all set of parameters to quickly create attributes and customize their JPA mapping. Now let's say we want to specify that a book is written in a certain language. We can use Forge to quickly create a Java enum and then have it as a JPA Enumerated in the `Book` entity :
   
  -[code, script]
  +[code, console]
   ----
   [Book.java]$ java-new-enum --named Language --targetPackage org.cdbookstore.model
   [Language.java]$ java-new-enum-const ENGLISH
  
positive.code: 
  Forge takes care of all the JPA relational mapping between both entities. Now, on an entity, we can add Bean Validation constraints on properties with the `constraint-add` command.
  
  [code, script]
  ----
  [Book.java]$ constraint-add --constraint NotNull --onProperty title
  [Book.java]$ constraint-add --constraint Past --onProperty publicationDate
  
negative.code: 
  To create a new JPA entity, let's use the `jpa-new-entity` command : 
  
  [code, console]
  ----
  [cdbookstore]$ jpa-new-entity --named Book
  ----
  