Catch all Exceptions and also return custom Errors in Jersey

Question

I want to catch all unexpected Exceptions in a jersey rest service. Therefore i wrote an ExceptionMapper:

@Provider public class ExceptionMapper implements javax.ws.rs.ext.ExceptionMapper<Exception> {     private static Logger logger = LogManager.getLogManager().getLogger(ExceptionMapper.class.getName());      @Override     public Response toResponse(Exception e) {         logger.log(Level.SEVERE, e.getMessage(), e);          return Response.status(Response.Status.INTERNAL_SERVER_ERROR).entity("Internal error").type("text/plain").build();     } } 

The mapper catches really all exceptions. Therefore i can't write:

public MyResult getById(@PathParam("id")) {     if (checkAnyThing) {         return new MyResult();     }     else {         throw new WebApplicationException(Response.Status.NOT_FOUND);     } } 

This is catched by the Mapper. Now i have to write:

public Response getById(@PathParam("id") {     if (checkAnyThing) { {         return Response.ok().entity(new MyResult()).build();     }     else {         return Response.status(Response.Status.NOT_FOUND).build();     } } 

Is this the correct way to catch all unexpected exceptions and also return errors (error codes) in jersey? Or is there any other (more correct) way?

Answer 1

WebApplicationException has a getResponse from which we can get the Response. So you can check for a WebApplicationException in your mapper. Maybe something like

@Override public Response toResponse(Throwable error) {     Response response;     if (error instanceof WebApplicationException) {         WebApplicationException webEx = (WebApplicationException)error;         response = webEx.getResponse();     } else {         response = Response.status(Response.Status.INTERNAL_SERVER_ERROR)                 .entity("Internal error").type("text/plain").build();     }     return response; } 

That way an instance of WebApplicationException thrown will just return the default response. This will actually handle some other exceptions also, not thrown explictly by your application. WebApplicationException has a few other exception under its hierarchy that are thrown by JAX-RS, for which predefined response/status codes are wrapped.

Exception                      Status code    Description ------------------------------------------------------------------------------- BadRequestException            400            Malformed message NotAuthorizedException         401            Authentication failure ForbiddenException             403            Not permitted to access NotFoundException              404            Couldn’t find resource NotAllowedException            405            HTTP method not supported NotAcceptableException         406            Client media type requested                                                              not supported NotSupportedException          415            Client posted media type                                                              not supported InternalServerErrorException   500            General server error ServiceUnavailableException    503            Server is temporarily unavailable                                                              or busy 

That being said, we could explicitly throw any of these exceptions in our code, just to give it more semantic value.

Generally speaking though, the example above may be unnecessary, unless you want to alter the response message/status code, as one can from the table above, the hierarchy of exceptions already have some general mapping. And in most cases, unexpected exceptions will already be mapped to InternalServerErrorException