How to catch exception from Servlet in error.jsp

[James Long]

Can any one tell me:
How to catch exception from Servlet in error.jsp page in order to show an error message to user if there is something wrong when execute the Servlet.
In Servlet I use:
if(something wrong){
throw new Exception("Something wrong");
}
The error message always not show in error.jsp page
instead it show in a new page with system generate error
message, which is not user friendly.
How can catch it using error.jsp?

Thank you in advance!!
Long

[Bharatesh H Kakamari]

First of all you cannot use a generic Exception class as in your code :

if(something wrong){
   throw new Exception("Something wrong");
}

Create your Exception class (eg YourException.class) that extends the Exception class. Then change the above code to YourException instead of Exception.
I think you have defined error.jsp to solve this problem. But in the case of JSPs even through it converts to a class file at runtime, you do not know the same of the .class file it generates. Thus error.jsp will not solve this problem.
Alternately you can use the <jsp:forward> with <jsp arams> to pass the error-message with your error.jsp.
HTH

[Bharatesh H Kakamari]

I do not know how that smiley came. It is params. Sorry if any one misinterprets.

[Bharatesh H Kakamari]

Instead of <jsp:forward> you can use RequestDispatcher forward() method to forward control to another jsp, servlet from a servlet.
HTH

[Bharatesh H Kakamari]

Just an example :

protected void sendErrorRedirect(HttpServletRequest request,
   HttpServletResponse response, String errorPageURL, 
   Throwable e)
       throws ServletException, IOException {
    request.setAttribute ("javax.servlet.jsp.jspException", e);
    getServletConfig().getServletContext().
     getRequestDispatcher(errorPageURL).forward(request, 
       response);
}
public void doPost(HttpServletRequest request,
   HttpServletResponse response) {
 try {
 // do something
 } catch (Exception ex) {
  try {
   sendErrorRedirect(request,response,"/jsp/MyErrorPage.jsp",ex);
  } catch (Exception e) {
   e.printStackTrace();
  }
 }
}

[James Long]

Bharatesh H Kakamari:
Sorry to respond late to you!
Your help is very valuable. Thank you very much!!!
I have another question is that:
I have a DoSomethingServlet to created a MyBean object and put it into session object, then DoSomethingServlet foward request to showMyBean.jsp page the show the result.
At the beginning of showMyBean.jsp I coded the following:
============
<jsp:useBean id="myBean" class="package.MyBean"
cope="session"/>

<%if(session.getAttribute("myBean") != null){
myBean = (MyBean)session.getAttribute("myBean");

if(myBean == null){
System.out.println("The sessin object is null now")
%>
<jsp:forward page="/MyApp/servlet/DoSomethingServlet" />
============
I check the session myBean if there is one,
then I get the MyBean object from the session.
Then check if the MyBean object is null
then I foward request to the DoSomethingServlet to
do something and create MyBean object and put into session
object again.
======
The problem occurs when I have not touched the showBean.jsp page in the browser for certain minutes (30? 20? minutes), the session may be time out, and I click a link in the jsp page for
this showMyBean.jsp page.
The result is a blank page show in the broswer instead of the new showMyBean.jsp page and I check console which show "The sessin object is null now" message.
My question is why
<jsp:forward page="/MyApp/servlet/DoSomethingServlet" />
doesn't work for me at this situation???
How can I get the new showMyBean.jsp page,
i.e. how can I invoke DoSomethingServlet again?
Anything wrong???
If any one, can tell me how to solve this problem. It would be very appriciated!
Thank you in advance!
J. Long