Hi,
I have a problem with how nulls are being handled by jersey and jaxb. I have a number of end-points in my web-service that can return null if no result is found for the request. At the moment this results in some JAXB exception and then jersey converts it to an HTTP 500 status.
The only way I have found to handle this situation is to throw an EntityNotFoundException. This was ok, although not great, as long as I returned a HTTP 404 status. This started getting more complicated as recently we have wanted to make sure we can differentiate, from the client side, between functional and technical 404's.
So three options present themselves.
1. Add some kind of header tag to 404s that are the result of the application completing the call but finding nothing to return. This makes it possible to distinguish if nothing was found because server is down or if provided ID does not exist.
2. Return some other http status that we will know is to be mapped to entity not found.
3. Return something that is semantically correct. With collections I can return an empty list (<MyEntities/>) without problems so I should be able to return <MyEntity/>. It is valid XML and the Jersey client does convert that to a null.
Choice 1 is interesting but requires sophisticated error handling by the client for something that is not, after all, an error or an exception.
Choice 2 breaks REST and general web conventions by overloading the meaning of existing http status. The best type I have found in the list of specified types is 204 - NO CONTENT. But when I read about intended purpose it fails to represent my use-case.
Choice 3 is ideal because it fits my API requirements and seems elegant and semantically correct. But the only way I have found to implement it is a bit strange. It relies on using exception handling.
I do the following:
* Implemented NotFoundException and ExceptionMapper approach as stated in section 2.8 of the user guide(
http://jersey.java.net/nonav/documentation/latest/jax-rs.html#d4e418)
* Rather than return a 404 exception I return a 200 status with an empty tag <MyEntity>
I have a few issues with this approach:
* In my view exception handling should not be used for implementing functionality.
* It doesn't scale very well
o I have to add code for each entity type I want to handle
o I have not figured out how I could create a response based on the wanted mime-type(xml, json, fastinfoset,etc)
* I could write my own message body writers but then I would lose that perfectly fine support I am getting from JAXB.
Is there something I am missing? Is there a better way to address this issue?
Cheers,
Florian
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