How I return HTTP 404 JSON/XML response in JAX-RS (Jersey) on Tomcat?

Your @Produces annotation is ignored because uncaught exceptions are processed by the jax-rs runtime using a predefined (default) ExceptionMapper If you want to customize the returned message in case of a specific exception you can create your own ExceptionMapper to handle it. In your case you need one to handle the NotFoundException exception and query the “accept” header for the requested type of the response:

@Provider
public class NotFoundExceptionHandler implements ExceptionMapper<NotFoundException>{

    @Context
    private HttpHeaders headers;

    public Response toResponse(NotFoundException ex){
        return Response.status(404).entity(yourMessage).type( getAcceptType()).build();
    }

    private String getAcceptType(){
         List<MediaType> accepts = headers.getAcceptableMediaTypes();
         if (accepts!=null && accepts.size() > 0) {
             //choose one
         }else {
             //return a default one like Application/json
         }
    }
}