How to handle grails exceptions in an ajax request? - grails

Question

If I am making a regular request I can define handling of errors and exceptions in UrlMappings.groovy as in the following example:
"403"(controller: 'error', action: 'index', params:['code':'403'])
"404"(controller: 'error', action: 'index', params:['code':'404'])
"500"(controller: 'error', action: 'index', params:['code':'500'])
"500"(controller: 'home', action: 'noPrivileges', exception: IllegalOperationException)
I can then handle the errors in a specific controller and render a view of my choice e.g.
class ErrorController {
def index = {
render view: "/errors/myErrorPage", model: [code: params.code]
}
}
This works perfectly and whenever there is an error on server I get my error page.
Now how can I achieve the very same behavior for ajax requests? I am making ajax requests either with grails remoteFunction or formRemote. Everytime when an exception occurs on the server, I want to execute the same piece of code in javascript (e.g. I want to show an alert with alert('There was an exception')).
The above described approach does not work for ajax requests. I still get back an error and even though there is content of myErrorPage.gsp in the error, it is not printed into the html element which I specified with update parameter of formRemote or remoteFunction.

Answer 1

I finally found a perfectly clean solution compatible with the approach which is used for handling standard requests.
You need to modify action which is handling the error as in the following example:
class ErrorController {
def index = {
if (request.xhr) {
response.status = 200
render template: "/errors/myAjaxErrorTemplate", model: [code: params.code]
} else {
render view: "/errors/myErrorPage", model: [code: params.code]
}
}
}
With request.xhr you can differentiate between ajax request and a standard request. In ajax request you further need to tell grails that the response is OK with setting response status to 200.
Very nice and clean. :) I am surprised this can't be googled anywhere...

Answer 2

The remoteFunction trigger a couple of events onFailure and on_ERROR_CODE. You can use that events to show your warning messages.
You can see more details in docs

Answer 3

If the request status is set correctly you could define an JavaScript function via the onFailure attribute of remoteFunction/formRemote.
Within this function you could handle your exception on client side.
Using the sample from the docs it could look like this:
<select onchange="${remoteFunction(action: 'bookByName',
update: [success: 'great', failure: 'ohno'],
params: '\'bookName=\' + this.value'),
onFailure: 'handleError'}">
<option>first</option>
<option>second</option>
</select>