anchor.diff:  
   This command generates a Maven structure importing the JSON and validation support.
   
  -== Accessing the validator
  +== Accessing the Validator
   
  -Edit the `org.acme.validation.BookResource` class, and inject the `validator` object as follows:
  +Edit the `org.acme.validation.BookResource` class, and inject the `Validator` object as follows:
   
   [source,java]
   ----
  
positive.code: It indicates it consumes and produces JSON.
  The method parameter (`book`) is created from the JSON payload automatically.
  
  The method uses the `validator` to check the payload.
  It returns a set of violations.
  If this set is empty, it means the object is valid.
  
  Let's now create the `Result` class as an inner class:
  
  
negative.code:     public void setPages(double pages) {
          this.pages = pages;
      }
  }
  ----
  
  