Application Exceptions for User Feedback

Question

Hi all!
I guess this is a best practice question.
I have a struts-based web app that contains various forms and fields that the user can interact with. When a user is filling out a form, I want to validate that the information s/he is inputting is correct. Now, for basic validation (valid date, string, number, etc) I plan on using javascript. However, there are some instances where I need to allow the user to submit the form, perform some action in my Action servlet and check to see if the data being submitted is correct (for instance, if a user is submitting a item, I would check against my session object, DB, EJB, etc, to see if it already exists). Now if somewhere down the stack of my methods, a piece of the submitted data is found to be invalid, I want to somehow feed back to the user that this is so by displaying it in a status section on my JSP.
From what I've read, it looks like I'm dealing with an application exception. So here's what I've come up with:
//Here's an application exception I created
public class MyAppException extends Exception {
     String errorCode;
     String errorDescription;
     public MyAppException () {
          super();
     public MyAppException (
          String pErrorDescription) {
          errorCode = null;
          errorDescription = pErrorDescription.toUpperCase();
     public MyAppException (
          String pErrorCode,
          String pErrorDescription) {
          errorCode = pErrorCode.toUpperCase();
          errorDescription = pErrorDescription.toUpperCase();
     //Gets...
     public String getErrorCode() {
          return this.errorCode;
     public String getErrorDescription() {
          return this.errorDescription;
//And here's the code that uses it
public class ThisAction extends AdmAction {
public ActionForward perform(
     ActionMapping          pMapping,
     ActionForm               pForm,
     HttpServletRequest pRequest,
     HttpServletResponse pResponse) throws ServletException {
try{
this.doSomething();
catch (MyAppException e){
pRequest.setAttribute("aToUsrMsg", e.getErrorDescription());
catch (Exception e){
e.printStackTrace();
public void doSomething() throws MyAppException, Exception{
try{
SomeClass.someMethod();
catch(MyAppException e){
throw new MyAppException(e.getErrorDescription());
catch(Exception e){
e.printStackTrace();
throw new Exception(e.getMessage());
public static class SomeClass throws MyAppException, Exception{
public static someMethod(
try{
if (SomeConditionExists){
throw new MyAppException("You did something wrong");
catch(Exception e){
throw new Exception("Unexpected:" + e.fillInStackTrace());
The problem instead of the application continuing as it should, reporting the app exception to the user, it halts and prints out the stack trace. Am I approaching this incorrectly?
Thanks for your help!
Leo

Answer 1

try{
if (SomeConditionExists){
throw new MyAppException("You did something wrong"); // (1)
catch(Exception e){ // (2)
throw new Exception("Unexpected:" + e.fillInStackTrace());
}Since MyAppException extends Exception, if MyAppException is thrown in (1), it will be caught in (2) and will later get "converted" to an ordinary Exception.