title: Grails- Exception when rendering Joda dates as JSON
body: <p>I'm trying to render command validation errors as json but I'm getting an exception. The command object is using joda time DateTime objects instead of java.util Date objects. The code to do the json rendering looks like:</p>
  
  <pre><code>def results = eventSaleDataCommand.errors.fieldErrors.toList()
  def errors = []
  for (error in results) {
      errors.add([
          'type'          : 'invalid_entry',
          'field'         : error.field,
          'rejected_value': error.rejectedValue,
          'message'       : error.defaultMessage
      ])
  }
  render errors as JSON
  </code></pre>
  
  <p>The exception I'm getting is:
  <code>Class org.codehaus.groovy.grails.web.converters.marshaller.json.GenericJavaBeanMarshaller can not access a member of class org.joda.time.tz.DateTimeZoneBuilder$PrecalculatedZone with modifiers "public".</code></p>
  
  <p>Anyone know how to get around this?</p>