Rescuing from REXML::ParseException

Hello,

When I call an action with some invalid XML or JSON data a parse
exception gets raised from within Rails/Ruby (REXML or
ActiveSupport::JSON). The problem that I’ve got is how to handle these
exceptions. In my application_controller.rb I have the following for
debugging purposes:

def rescue_action_in_public(exception)
respond_to do |request|
request.all { render :text => “Uh oh” }
end
end

and the same for #rescue_action_locally. It seems that if the Content-
Type header of the request is set to application/xml or application/
json then Rails ignores my exception rescuing code and goes back a
FAILSAFE 500 error. Anyone know why this is or what I’m doing wrong?

Thanks

Hi Alistair,

On Fri, 2009-08-14 at 08:13 -0700, subv3 wrote:

Hello,

When I call an action with some invalid XML or JSON data a parse
exception gets raised from within Rails/Ruby (REXML or
ActiveSupport::JSON). The problem that I’ve got is how to handle these
exceptions. In my application_controller.rb I have the following for
debugging purposes:

def rescue_action_in_public(exception)
respond_to do |request|
request.all { render :text => “Uh oh” }
end
end

and the same for #rescue_action_locally. It seems that if the Content-
Type header of the request is set to application/xml or application/
json then Rails ignores my exception rescuing code and goes back a
FAILSAFE 500 error. Anyone know why this is or what I’m doing wrong?

No conclusive answer, but a couple of suggestions that might help move
you along… First, I’d get this working in a specific controller
before moving it to application.rb. Second, ‘request’ refers to the
request object and might get you into trouble here. Lastly, from
looking at the respond_to source, it looks like the ‘catch all’ type
specifier is ‘any’, not ‘all’. But I could be reading it wrong. You
might want to take a look.

HTH,
Bill

Hi Bill,

The problem isn’t in the respond_to block. Even a straight call to
render some text without using respond_to still falls back to the
FAILSAFE 500 error.

Cheers

On Aug 14, 11:13 am, subv3 [email protected] wrote: […]

bleh, need to read the thread title. Either way, changed make_ish to

raise REXML::ParseException

exception is still being rescued as expected :\ what’s missing?

On Aug 14, 11:13 am, subv3 [email protected] wrote:

request.all { render :text => "Uh oh" }

end
end

and the same for #rescue_action_locally. It seems that if the Content-
Type header of the request is set to application/xml or application/
json then Rails ignores my exception rescuing code and goes back a
FAILSAFE 500 error. Anyone know why this is or what I’m doing wrong?

Thanks

What is the actual exception being raised? I’m having trouble
reproducing this:

class TotalController < ApplicationController
def blow_up
respond_to do |wants|
wants.json { render :json => make_ish }
wants.html { render :text => “hello” }
end
end

def rescue_action_locally(e)
render :text => “resuced”
end

private
def make_ish
raise “it up”
{:yo => :max!}
end
end

map.connect “die.:format”, :controller => “total”, :action =>
“blow_up”

[email protected]:~$ wget http://amrita/pixie/die.html
–2009-08-14 16:34:26-- http://amrita/pixie/die.html
Resolving amrita… 127.0.1.1
Connecting to amrita|127.0.1.1|:80… connected.
HTTP request sent, awaiting response… 200 OK
Length: 6 [text/html]
Saving to: `die.html’

2009-08-14 16:34:26 (925 KB/s) - `die.html’ saved [6/6]

[email protected]:~$ cat die.html
hello

[email protected]:~$ wget http://amrita/pixie/die.json
–2009-08-14 16:34:34-- http://amrita/pixie/die.json
Resolving amrita… 127.0.1.1
Connecting to amrita|127.0.1.1|:80… connected.
HTTP request sent, awaiting response… 200 OK
Length: 8 [application/json]
Saving to: `die.json’

2009-08-14 16:34:34 (913 KB/s) - `die.json’ saved [8/8]

[email protected]:~$ cat die.json
resuced
[email protected]:~$

As you can see, rescue_action_locally is being called, and the content-
type of the response is set to application/json. Or does it look there
theres something my setup is missing that yours has?

Typo… change = chance

For anyone else browsing this discussion.
http://groups.google.co.uk/group/northwest-tech-startup/browse_thread/thread/d97334ed0fcee2d8
is tackling the same problem but came up with no solution.

I think the exception I’m dealing with happens before it has a change
to get caught by the rescue_action* methods. Maybe my backtrace will
give some insight.

http://gist.github.com/168372

in case anybody gets here waiting for an answer try the following
plugin to deal with XML/JSON parse errors :

http://github.com/kares/request_exception_handler

I’ve decided to bypass ActionPack and use Rails metal instead (I was
going to use it for this eventually anyway its an API which needs to
be fast). Now I can parse the parameters myself in Rack and rescue
incoming requests that send invalid JSON/XML data nicely.

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