Return partial Domain Class

Reading the description of GRAILS-5791, I found this interesting question. The asker expects the JSON returned by "domain as JSON" not including some properties he lists.
There are serval solutions, the comments following that question have list two ones. Here I will give my own one. In my way, I will add one method to the domain classes in the grails app: part, which returns a map including or excluding some properties of a domain class. Then you can render the result map as JSON. The following shows how to use this method:

  def job= Job.get(1)

 //include
 render job.part(include:['categorys', 'source']) as JSON

 //except
 render job.part(except:['id', 'version']) as JSON

This sample is very intuitive. The first statement will result in a JSON only including categorys and source; the JSON rendered by second statement will include all the properties of the domain class except id and version.
Using part, you can make your life easier and also make your code more grace.
Now, let's see how to adding the part method to the domain classes:

• how: In groovy, in order to add a method to an object dynamiclly, we can use mop.
• when: In grail app, there is a file named BootStrap.groovy, where is a good place to do some initialization works.

When we know how and when to do that job, here is the detail:

import org.codehaus.groovy.grails.orm.hibernate.support.ClosureEventTriggeringInterceptor as Events

class BootStrap {
 def grailsApplication

 def excludedProps = [Events.ONLOAD_EVENT,
    Events.BEFORE_DELETE_EVENT, Events.AFTER_DELETE_EVENT,
    Events.BEFORE_INSERT_EVENT, Events.AFTER_INSERT_EVENT,
    Events.BEFORE_UPDATE_EVENT, Events.AFTER_UPDATE_EVENT]

  def init = { servletContext ->
     grailsApplication.domainClasses.each{ domainClass ->
         domainClass.metaClass.part= { m ->
             def map= [:]
             if(m.'include'){
                 m.'include'.each{
                     map[it]= delegate."${it}"
                 }
             }else if(m.'except'){
                 m.'except'.addAll excludedProps
                 def props= domainClass.persistentProperties.findAll {
                     !(it.name in m.'except')
                 }
                 props.each{
                     map[it.name]= delegate."${it.name}"
                 }
             }
             return map
         }
     }
  }
  def destroy = {
  }
}

You also can change this to a plugin, then you can use this feature across different grails apps. Hope you enjoy this.