There are a few things I'd like to point out to add to this example:
1) JAX-RS is still new. In the future, they might improve the exception handling or whatnot (so if you return null, they might decided to return 404 ... who knows)
2) We can always wrap all JAX-RS with a Filter. So you can throw JPA level exception (not found) and let the filter catch it and convert it to WebApplicationException(404). Thus in theory, your JAX-RS implementation won't have any RuntimeException explicitly in the code.
There are a few things I'd like to point out to add to this example:
1) JAX-RS is still new. In the future, they might improve the exception handling or whatnot (so if you return null, they might decided to return 404 ... who knows)
2) We can always wrap all JAX-RS with a Filter. So you can throw JPA level exception (not found) and let the filter catch it and convert it to WebApplicationException(404). Thus in theory, your JAX-RS implementation won't have any RuntimeException explicitly in the code.