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I'm migrating some servlets over to the Spring framework, using Spring MVC. Currently in each servlet we authenticate the user and if the authentication fails we do this:
if (authfailed)
{
response.sendError(HttpServletResponse.SC_UNAUTHORIZED,
"You are not authorized.");
return;
}
On the front end is a YUI-based application, and when an error status is returned the "failure" callback displays a dialog with the error message given above.
I know in my controller I can get the response object and call sendError, but is that the best way to handle this? sendError also throws an IOException so I'd have to catch that - a bit of annoying code to insert in every method of every controller.
I have the same problem handling exceptions - the servlets have try-catch blocks that call sendError in the catch method. I know I can mark my exception handlers with
@ExceptionHandler
@ResponseStatus(value = HttpStatus.NOT_FOUND)
but doesn't the exception handling class need to be in each controller class?
Finally, if the exception happens in a service called from a controller, does the exception bubble up to the controller or should I handle the exception in the service (thus pushing these exception handling issues into the service layer)?
This seems more difficult than it should be, but as with many things in Spring it's likely I don't understand what's going on. All I want to do is to send an error status and message back in the response!
Thanks,
Paul
409
It looks like you have the most of the answers in your question itself :)
To reiterate,
Have the controller like this
@RequestMapping("/test")
public String verifyAuth(HttpServletRequest request) throws NotFoundException {
String id = request.getParameter("id");
if (id == null)
throw new NotFoundException("Id not found in the request");
return "success";
}
Declare the exception class in NotFoundException.java,
@ResponseStatus(value=HttpStatus.NOT_FOUND, reason="Id Not Found")
public class NotFoundException extends Exception {
public NotFoundException(String msg) {
super(msg);
}
}
This exception class need not be every controller class. Declare it as public class and import it in every required controller.
This is one way of doing it. If you like the non-spring style, declare HttpServletResponse in every controller arguments and do
@RequestMapping("/test")
public String verifyAuth(HttpServletRequest request, HttpServletResponse response) {
...
try {
response.sendError(..)
catch(..) {}
}
Or you can use views to show error message,
@RequestMapping("/test")
public String verifyAuth(HttpServletRequest request, Map<String, Object> map){
String id = request.getParameter("id");
if (id == null) {
map.put("status", HttpStatus.NOTFOUND);
map.put("reason", "Id Not Found");
return "error"
}
return "success";
}
Make sure your viewResolver is configured correctly and in the error.jsp to get the error string, you could say.
<body>
${status} ${reason}
</body>
Define error.jsp with nice css for all kind of errors you would expect. These are not the only ways. With spring you have freedom to do anything. I have seen few ppl rendering json object for error message.
To answer your another question of if the error happens in the service called by the controller is depend on your scenario. For example you are trying to read the user store, if the user store not available error happens, I would handle there itself to read from another replica user store if one available and If I found user does not exist I would leave the exception to the controller to throw.
143
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