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Posted to user@struts.apache.org by Brian McGovern <bm...@imediainc.com> on 2005/02/15 16:28:27 UTC

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

RE: Proper n tiered exception handling

Posted by Mark Bennett <ma...@ncmail.net>.
I think you are missing out on some usefull features by using this.  You
can't use the ActionMapping Parameter property to distinguish operations
<action ... parameter="add" ... />  and you will have to reimplement a
solution if you use DispatchAction.  I think there are benefits to
declaritive exception handling, flexibility.

Mark


-----Original Message-----
From: Ole Hildebrandt [mailto:OH@BWSolution.de]
Sent: Tuesday, February 15, 2005 12:21 PM
To: 'Struts Users Mailing List'
Subject: AW: Proper n tiered exception handling


Hi.

My personal opinion is, that the Struts Exception handling doesn't bring any
benefits.

I use an approch based on inheritance and the "Template Method"-Pattern from
the GoF:

I create an abstract Class extended from "Action". All application-Specific
Actions extend that class. The Abstract Action-class is responsible for
catching all Exceptions that were not explicitly catched by the extending
class.

Source-Snippet from the Abstact Class "AbstractContoller.java":

public abstract class AbstractController extends Action {

	//Template-Method. Calls "doExecute" on each Request and handles
uncaught Exceptions:
    public ActionForward execute(ActionMapping mapping, ActionForm form,
            HttpServletRequest request, HttpServletResponse response) {
        try {
            return doExecute(mapping,form, request,response);
        } catch (Throwable e) {
            request.setAttribute("messagekey","error.unknownError");
		log.error("Uncought Exception",e);
            return mapping.findForward("error");
        }
    }

//All extending classed implement this method
public abstract ActionForward doExecute(ActionMapping mapping, ActionForm
form,
            HttpServletRequest request, HttpServletResponse response) throws
Exception ;


And I use ExceptionChaining. See this article for more info:
http://www.javaworld.com/javaworld/jw-09-2001/jw-0914-exceptions.html?


Kind Regards

Ole

-----Ursprüngliche Nachricht-----
Von: Brian McGovern [mailto:bmcgovern@imediainc.com]
Gesendet: Dienstag, 15. Februar 2005 16:28
An: user@struts.apache.org
Betreff: 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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AW: Proper n tiered exception handling

Posted by Ole Hildebrandt <OH...@BWSolution.de>.
Hi.

My personal opinion is, that the Struts Exception handling doesn't bring any
benefits. 

I use an approch based on inheritance and the "Template Method"-Pattern from
the GoF:

I create an abstract Class extended from "Action". All application-Specific
Actions extend that class. The Abstract Action-class is responsible for
catching all Exceptions that were not explicitly catched by the extending
class. 

Source-Snippet from the Abstact Class "AbstractContoller.java":

public abstract class AbstractController extends Action {

	//Template-Method. Calls "doExecute" on each Request and handles
uncaught Exceptions:
    public ActionForward execute(ActionMapping mapping, ActionForm form,
            HttpServletRequest request, HttpServletResponse response) {
        try {
            return doExecute(mapping,form, request,response);
        } catch (Throwable e) {
            request.setAttribute("messagekey","error.unknownError");
		log.error("Uncought Exception",e);
            return mapping.findForward("error");
        }
    }

//All extending classed implement this method
public abstract ActionForward doExecute(ActionMapping mapping, ActionForm
form,
            HttpServletRequest request, HttpServletResponse response) throws
Exception ;
  

And I use ExceptionChaining. See this article for more info:
http://www.javaworld.com/javaworld/jw-09-2001/jw-0914-exceptions.html?


Kind Regards

Ole

-----Ursprüngliche Nachricht-----
Von: Brian McGovern [mailto:bmcgovern@imediainc.com] 
Gesendet: Dienstag, 15. Februar 2005 16:28
An: user@struts.apache.org
Betreff: 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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