Jersey/Jackson Exception problem with ExceptionMapper

I'm using Jersey to provide a java REST service to the outside world. I offer some functions that take JSON and I use the Jackson framework in combination with jersey to convert them into POJOs.

I have the problem that if wrong jackson format is sent to the server, the answer (content of the http response) is a jackson specific exception description. If I have a POJO with an attribute "surname" and send "sursname" in the json string to the server, I get:

Unrecognized field "sursname" (Class XY), not marked as ignorable at [Source: sun.net.httpserver.FixedLengthInputStream@903025; line: 1, column: 49] (through reference chain: XY["sursname"])

Thats quite ok, but I would like to have my own response content, for example my own error code. I already wrote a custom ExceptionMapper that should map all Throwables.

@Provider
public class WebserviceExceptionMapper implements ExceptionMapper<Throwable> {

@Override
public Response toResponse(Exception e) {
    e.printStackTrace();
    return Response.status(400).entity("{\"errorcode\":\"CRITICAL_ERROR\"}").type(MediaType.APPLICATION_JSON).build();
    }
}

It seems that the jackson exception is thrown before my webservice method is called, so i have no chance to map it?

Does anyone have an idea? Big thanks und sorry for my english ;)