Question

I am having a question that how can I send JSON Object from Springs MVC so that I can convert it into a JavaScript Object on my HTML Page.

In a traditional way I do it: Below is a snippet from Java Servlet which sets a request attribute and forward it to the JSP Page.

   JSONObject jsonObj = new JSONObject();
   jsonObj.put("name","test");
   jsonObj.put("age",24);
   request.setAttribute("jsonObj",jsonObj);
   request.getRequestDispatcher("test.jsp").forward(request,response);

In JSP I retrieve as :

   <script type="text/javascript">
    var jsonObj =<%=request.getAttribute("jsonObj"); %>;
    alert("name = "+jsonObj.name+" ; age = "+jsonObj.age); // This will output name and age from the JSON Object
   </script>

So what I need to ask how can I do the same in Springs MVC. How can I send the JSONObject from Dispatcher Servlet, and convert it to JS object in my JSP page ?

Answer 1

An easy way to do this using the ObjectMapper. It will create an JSON String from your Object. And that you can send to your view/jsp.

I put an small example of a controller I do this (just snipped).

@Controller
public class UsersSettingsController {

    @Autowired
    UserSettingsDefaultService userSettingsService;


    @RequestMapping(value="/userSettings/dynamic/userSettings", method=RequestMethod.GET)
    public ModelAndView get() throws Exception {
        ModelAndView mav = new ModelAndView();
        ObjectMapper mapper = new ObjectMapper();


    User user = (User)SecurityContextHolder.getContext().getAuthentication().getPrincipal();
    UserSettings userSet = userSettingsService.getUserSettingsByUser(user);

    mav.addObject("userSettingsJSON", mapper.writeValueAsString(userSet));

    mav.setViewName("userSettings/dynamic/filter");


        return mav;
    }
}

Or course can you create your JSON Object in your Contoller step by step like you did in your example. Then you don’t need the Mapper, just sending the String to your View.

In the JSP you load the json String like this into a JS var:

var jsonString = '${userSettingsJSON}';

To get elements from JSON String or parse, see: http://www.json.org/js.html.
I’m an KnockOut Framework Fan would do it with it.