spring - Best way to handle errors and messages in Grails service -

i have grails app, , want know best way pass errors , messages service layer controller. example, click link in app calls service , brings me new page. on new page in application, want see list of messages so:

information: 10 files processed successfully.  warning: filea missing creationdate  error: fileb failed processing error: filec failed processing error: filed failed processing 

i know can create custom object "servicereturnobject" properties like:

def data def errors def warnings def information 

and have of services return object.

i know can use exceptions, not sure if right solution multiple exceptions , multiple types of exceptions.

what best practice here? examples helpful, thanks.

to return errors, create custom exception class, , use wrap other errors service can generate. way, need catch limited number of exceptions. if have more 1 controller method/closure needs return errors, factor code this:

first, create exception class , put in src/java in right namespace:

class myexception extends exception {     protected string code; // make int if want     public string getcode() { return code; }      public myexception(string code, string message) {         super(message);         this.code = code;     } } 

now, in controller, create error-handling method , wrap calls in it

class mycontroller {     def myservice;      def executesafely(closure c) {         map resp = [:]         try {             resp.data = c();         }         catch(myexception myex) {             resp.error = myex.getmessage();             resp.code = myex.getcode();         }         catch(exception ex) {             resp.error = 'unexpected error: ' + ex.getmessage();             resp.code = 'foo';         }          return resp;     }       def action1 = {         def resp = executesafely {             myservice.dosomething(params);         }          render resp json;     }      def action2 = {         def resp = executesafely {             myservice.dosomethingelse(params);         }          render resp json;     } } 

alternatively, can have executesafely convert response json , render directly.