Re: What to do when an exception is thrown during ajax rendering?

From: Andy Schwartz <>
Date: Fri, 07 Feb 2014 13:22:24 -0500

Hi Ed -

On 2/6/14 4:14 PM, Edward Burns wrote:
> If #{bean.throwExceptionOnAjax} throws an exception? What should happen
> to the handleError()? It should get invoked, right?


> Well, it doesn't. Instead, we get an exception about nested CDATA.
> That's the first problem.
> Once we fix the nested CDATA problem, we now see that the error handler
> is not invoked because the status is not set to 500.
> Here are my questions to the community.
> Should an exception occurring during render cause an HTTP 500 error to
> be set as the status of the Ajax response?

Would that require buffering up the entire response just in case we end
up needing to call sendError(500)? If so, I would rather that we not do

> Should we allow the ajax error handler to take effect when the rendering
> contains broken CDATA rendered response text?

Seems reasonable.

> I have a patch that makes it so both of things are true.

How do you set the response status code after rendering has started?

> Here is the partial Ajax response with the proposed fix in place:
> <?xml version='1.0' encoding='UTF-8'?>
> <partial-response id="j_id1">
> <changes>
> <update id="willThrowException">
> <![CDATA[
> <partial-response id="j_id1">

This would be something like "<span id="j_id1">" as opposed to a nested
<partial-response> element, right?

> ]]>
> </update>
> </changes>
> <error>
> <error-name>class java.lang.RuntimeException</error-name>
> <error-message>
> <![CDATA[
> Intentionally throwing exception on ajax request
> ]]>
> </error-message>
> </error>
> </partial-response>
> Is this ok?

Sounds fine. Does the xsd for partial response payloads allow this?

Would we attempt to apply the <changes> if an <error> is present later
on in the payload?

If the <changes> content contains invalid content (cannot be parsed), do
we call the error handler? If yes, does the error handler get called
twice (once for the invalid <changes> content and again for the <error>)?


> Ed