I probably have not shown you enough in terms of setup. There is more to
configure this completely. I will try to outline this shortly. To answer your
question , I don't rethrow anything. It's not necessary. Your struts actions
have the following signature:
public ActionForward execute(ActionMapping mapping, ActionForm form,
HttpServletRequest req, HttpServletResponse resp)
throws Exception
{
.......
}
Any exception thrown within this method with propagate up through the exception
handling framework. Whether it's a SQLException, RemoteException or any
checked or runtime exception will flow upward. You delcare where to forward to
(what page). I designed a generic error handling jsp, because I did not want
to design a separate JSP for every type of exception. This is a preference
thing. My way was right for me. Here is my JSP for handling errors:
<[EMAIL PROTECTED] import="java.util.*" %>
<[EMAIL PROTECTED] uri="/WEB-INF/taglibs-log.tld" prefix="log" %>
<[EMAIL PROTECTED] uri="/WEB-INF/fmt.tld" prefix="fmt" %>
<[EMAIL PROTECTED] uri="/WEB-INF/c.tld" prefix="c" %>
<%@ taglib uri="/WEB-INF/struts-html.tld" prefix="html" %>
<%
Throwable t =
(Throwable)request.getAttribute("org.apache.struts.action.EXCEPTION");
if ( t!= null)
{
StackTraceElement [] trace = t.getStackTrace();
int size = trace.length;
out.print("<!--\n\n");
out.print(t.toString());out.print("\n");
for (int i=0; i < size; i++)
{
out.print(trace[i].toString());
out.print("\n");
}
out.print("\n\n-->");
}
%>
<!-- #BeginEditable "body" -->
<!-- center box header image -->
<div id="centerBoxTopErrorTall2">System Error</div>
<!-- begin center box content stretch image -->
<div id="centerBoxStretch2">
<table width="95%" border="0" cellpadding="0" cellspacing="0">
<tr >
<td>
<div id="infoBoxError">
<!-- left nested inside infobox -->
<html:errors
bundle="systemerrorbundle"/>
</div>
</td>
</tr>
</table>
</div>
<!-- end center box content stretch image -->
<!-- center box content footer image -->
<div id="centerBoxBtm2"> </div>
<!-- #EndEditable "body" -->
There's more to this story. Notice the line:
<html:errors bundle="systemerrorbundle"/>
This is where I supply a customer message. The message is externalized in a
properties file for I18N. This is my syserror.jsp page which is referenced in
the struts.xml config.
-----Original Message-----
From: Brian McGovern <[EMAIL PROTECTED]>
Sent: Feb 15, 2005 11:24 AM
To: Struts Users Mailing List <user@struts.apache.org>, [EMAIL PROTECTED]
Subject: RE: Proper n tiered exception handling
Jim,
So in this approach you really dont use any try catch blocks at all? or you
just re - throw the original exception that you caught?
How do you grab the error on the JSP page?
Thanks
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
Sent: Tuesday, February 15, 2005 11:16 AM
To: Struts Users Mailing List
Subject: Re: Proper n tiered exception handling
I use declaritive exception handling which is built into Struts. Works great
for me. I really don't use custom exceptions that much any more because it's
harder to track the original error. Also, I don't clutter my code with alot of
try/catch blocks unless it's absolutely necessary. I allow all exceptions to
propagate through the Struts built-in exception handling framework.
Here is an example of declaritive exception handling in the struts config:
<global-exceptions>
<exception
key="error.application.nullpointer"
type="java.lang.NullPointerException"
path="/tmpl_main2.jsp?error=/error/null.jsp&pagetitle=error.title.key">
</exception>
<exception
key="error.application.parse"
type="java.text.ParseException"
path="/tmpl_main2.jsp?pageleft=/mainmenu.jsp&pagecenter=/error/syserror.jsp&pagetitle=error.title.key">
</exception>
<exception
key="error.application.import.zip"
type="java.util.zip.ZipException"
path="/tmpl_main2.jsp?pageleft=/mainmenu.jsp&pagecenter=/error/syserror.jsp&pagetitle=error.title.key">
</exception>
<exception
key="error.application.unhandled"
type="java.lang.Exception"
path="/tmpl_main2.jsp?pageleft=/mainmenu.jsp&pagecenter=/error/syserror.jsp&pagetitle=error.title.key">
</exception>
When these exception types are thrown, the user is forwarded to the proper
custom page. If your creative you can grab the current error and print the
stack trace as an HTML comment within the page for your review. You can then
view the exception stack trace by selecting view/source from you browser. Only
show the user and nice "pretty" message.
Jim
-----Original Message-----
From: Brian McGovern <[EMAIL PROTECTED]>
Sent: Feb 15, 2005 10:28 AM
To: user@struts.apache.org
Subject: Proper n tiered exception handling
I'm looking to get a handle on best exception handling practices in my app.
Kinda beginner question i guess, sorry.
Im catching the various sql and naming exceptions in the data classes and
logging and throwing a custom exception called ApplicationException which is
blank and provided below. I've read up but an still a little confused on how
exactly to build this exception class to extend the available struts exception
classes that would gracefully map to an error display jsp where i could display
the error to the user. Right now I just get the HTTP status 500 strack trace
on the screen.
Controller snippet that catches the data obj's thrown ApplicationException:
------------------------------------------------------------------------
try {
zRepBeanBn =
MyData.getRepByID(StringUtils.convertToInt(request.getParameter("RepID")));
}catch (ApplicationException zAppEx){
throw zAppEx;
}
------------------------------------------------------------------------
ApplicationException that needs work: How do I extend this?
------------------------------------------------------------------------
public class ApplicationException extends Exception {
public ApplicationException(String message) { }
}
------------------------------------------------------------------------
Thanks
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