@POST
 @Path("/class/{fullName}/instances")
 public Response addInstanceToClass(@PathParam("fullName") String fullName, String json) {
   Clazz clazz = LomBusinessFacade.getInstance().getClass(fullName);
   if (clazz != null) {
     try {
       ObjectNode instanceJson = (ObjectNode) jsonNodeFromString(json);
       Instance instance = Instance.instanceFromJson(instanceJson);
       instance.setClassID(clazz.getId());
       instance = LomBusinessFacade.getInstance().addInstance(instance);
       ResponseBuilderImpl builder = new ResponseBuilderImpl();
       builder.status(201);
       builder.entity(instance.getJson().toString());
       return builder.build();
     } catch (Exception e) {
       return Response.notAcceptable(null).build();
     }
   }
   return Response.notAcceptable(null).build();
 }