Grails error when customizing JSON output -

i modifying way grails converts object json. add in bootstrap.groovy:

json.registerobjectmarshaller(ufile) {              def returnarray = [:]             returnarray['id'] = it.id             returnarray['docname'] = it.docname             returnarray['fullpath'] = it.fullpath             returnarray['uploaddate'] = it.uploaddate             returnarray['mime'] = it.mime             returnarray['size'] = it.size             returnarray['eval'] = it.eval              return returnarray         } 

i ufile list database , try convert json:

def files = ufile.findall() def json = files json 

and have error:

class    org.codehaus.groovy.grails.web.converters.marshaller.json.genericjavabeanmarshaller can not access member of class org.springframework.beans.generictypeawarepropertydescriptor modifiers "public". stacktrace follows: message: class org.codehaus.groovy.grails.web.converters.marshaller.json.genericjavabeanmarshaller can not access member of class org.springframework.beans.generictypeawarepropertydescriptor modifiers "public" 

then when restart server error disappears , works should.

this ufile domain class:

class ufile {  string docname string fullpath integer size string mime date uploaddate = new date() boolean item   static hasmany = [metadatavalue : metadatavalue] static belongsto = [user: user]  static mapping = { }  static transients = ['eval']  static constraints = {      docname blank: false, nullable: false     metadatavalue nullable: true     fullpath blank: false, nullable: false     size blank: false, nullable: false     mime blank: false     user blank: false, nullable: false     item nullable: false       size validator: { size ->         if ( size > 536870912 ) return false     }  }  def geteval(){      def total = 0      if (user) {          user.validationops.each { op ->               def mv = metadatavalue.find { mv ->                 mv.metadata.element == op.metadata.element             }               total += (mv ? 1 : 0) * op.value          }          return user.totalpesos() == 0 ? 0 : total / user.totalpesos()      }      return total      } } 

anyone have idea why error? in advance !