[jax-rs-spec users] [jsr339-experts] Re: Re: WebApplicationException Response entity and exception mappers

From: Santiago Pericas-Geertsen <>
Date: Mon, 26 Nov 2012 10:45:00 -0500

On Nov 23, 2012, at 6:17 AM, Sergey Beryozkin <> wrote:

> On 20/11/12 14:04, Bill Burke wrote:
>> On 11/20/2012 5:42 AM, Sergey Beryozkin wrote:
>>> Let me summarize.
>>> One one hand the spec provides for the optimization in cases where WAE
>>> Response entity is not null. On the other hand, this optimization leads
>>> to the issue where an application code reports WAE with Response having
>>> an entity and also with the cause exception for the benefit of the WAE
>>> mapper.
>>> I'd like to propose one of the following:
>>> 1. Keep the current optimization in place but update the spec to say
>>> that "if WAE Response entity is null or WAE cause exception is not null
>>> - use the mapper, otherwise - use WAE Response entity directly"
>>> 2. Drop the optimization - I'd expect any custom mapper check WAE
>>> Response anyway before creating some custom Response instead and
>>> dropping this optimization would require a mapper to check if entity is
>>> not null - guess most of the mappers do it all the time anyway...
>> In Resteasy, we allow you to write a mapper for any exception class, so
>> I vote #2.
> Me too. I've thought about it more, I can see why the case for the optimization might work, however the case of supporting the WAE mappers seeing all WAEs for the purpose of not necessarily converting them to Responses but its own statistics/logging/etc purposes is stronger IMHO.
> It will indeed technically break the BC but at the expectation level only - the risk though seems pretty minimal and would affect only mappers not doing proper checks on WAE Response...
> It can be recommended at the spec level to get custom WAE mappers to check that Response entity is not null before trying to do its custom conversion if any.
> Furthermore, I'm assuming this 'expectation' issue can be handled at the RI level only by introducing a Jersey specific property that can be enabled to get the optimization still supported in cases where someone has indeed written a mapper which does immediate conversion without any checks...

 Although I have some concerns about BC, I can see the value of the proposed change. I gather from this discussion that Resteasy and CFX already do what's being proposed. Can you confirm?

-- Santiago