issues with xml in spring mvc 3

Question

See my following 4 simple examples, 2 works for xml, the other 2 does not.

//works for html, json, xml
     @RequestMapping(value = "/test", method = RequestMethod.GET)
            public ModelAndView testContentNegiotation(HttpServletRequest request, HttpServletResponse response) {

                ModelAndView mav = new ModelAndView();

                    TestTO test =  new TestTO("some msg", -888);
                    mav.addObject("test", test);

                    mav.setViewName("test"); //test is a jsp page

                return mav;
            }

---

//does not work for xml
     @RequestMapping(value = "/test", method = RequestMethod.GET)
            public ModelAndView testContentNegiotation(HttpServletRequest request, HttpServletResponse response) {

                ModelAndView mav = new ModelAndView();

                    ErrorTO error =  new ErrorTO("some error", -111);
                    mav.addObject("error",error );

                    TestTO test =  new TestTO("some msg", -888);
                    mav.addObject("test", test);

                    mav.setViewName("test");

                return mav;
            }

---

         //works for xml and json   
@RequestMapping(value = "/test3", method = RequestMethod.GET)
    public @ResponseBody ErrorTO test3(HttpServletRequest request, HttpServletResponse response) {

        ErrorTO error = new ErrorTO();
        error.setCode(-12345);
        error.setMessage("this is a test error.");
        return error;
    }

---

//does not work for xml
            @RequestMapping(value = "/testlist", method = RequestMethod.GET)
            public @ResponseBody List<ErrorTO> testList2(HttpServletRequest request, HttpServletResponse response) {

                    ErrorTO error =  new ErrorTO("an error", 1);
                    ErrorTO error2 =  new ErrorTO("another error", 2);
                    ArrayList<ErrorTO> list = new ArrayList<ErrorTO>();
                    list.add(error);
                    list.add(error2);
                    return list;

            }

In the two examples that can't produce xml, is it possible for configuring spring to make it work?

Answer 1

The two examples that don't generate XML aren't working because you have multiple top-level objects in your model. XML has no way to represent that - you need a single model object that can then be converted into XML. Similarly, a bare list cannot be converted into XML by Spring MVC.

In both cases, you need to wrap the various model objects into a single root object, and add that to the model.

JSON, on the other hand, has no issue with representing multiple top-level objects in a single document.