I'm new to mvc spring and I have some code from the internet like the following:
#RequestMapping(value = "/newContact", method = RequestMethod.GET)
public ModelAndView newContact(ModelAndView model) {
Contact newContact = new Contact();
model.addObject("contact", newContact);
model.setViewName("ContactForm");
return model;
}
#RequestMapping(value = "/saveContact", method = RequestMethod.POST)
public ModelAndView saveContact(#ModelAttribute Contact contact) {
contactDAO.saveOrUpdate(contact);
return new ModelAndView("redirect:/");
}
#RequestMapping(value = "/deleteContact", method = RequestMethod.GET)
public ModelAndView deleteContact(HttpServletRequest request) {
int contactId = Integer.parseInt(request.getParameter("id"));
contactDAO.delete(contactId);
return new ModelAndView("redirect:/");
}
My question is,
what is the purpose of using and using in any case with # ModelAttribute, ModelAndView mode and HttpServletRequest request?
Thanks you.
Please check https://stackoverflow.com/a/33422321/3530898. I my opinion ModelAttribute is used usually with form transport objects (i.e. bean classes whose fields contain the form data), ModelAndView is used when you want to set view name and model object in a single method of a controller. Both ModelAndView and Model uses HttpServletRequest internally, Spring has added wrapper classes over HttpServletRequest to make development easier for developer. But sometime you need HttpServletRequest class for instance, when you want to capture a query parameter in an Ajax call etc
Related
How do I make the objects associated to a RequestMapping in a controller be accessible by another RequestMapping in the same controller that returns to the same view page? Thank you.
Here is my sample code which is placed in only one controller:
#RequestMapping(value="firstMapping",method=RequestMethod.POST)
public ModelAndView firstMapping (HttpServletRequest request) {
//myObject is processed here
ModelAndView mav = new ModelAndView();
mav.setViewName("samplepage");
mav.addObject("myObject",myObject); //How do I pass this object to the mapping below?
return mav;
}
#RequestMapping(value="secondMapping",method=RequestMethod.POST)
public ModelAndView secondMapping (HttpServletRequest request) {
//I want to do something else here but I need the object from
//the mapping above. For example myObject2 is processed here
ModelAndView mav = new ModelAndView();
mav.setViewName("samplepage");
mav.addObject("myObject",myObject);
mav.addObject("myObject2",myObject2);
return mav;
}
In the first method, instead of setting a view you should forward the request to the second method after setting the attribute.Set view in second method.By using this request is forwarded to the second method after processing.
#RequestMapping(value="firstMapping",method=RequestMethod.POST)
public ModelAndView firstMapping (HttpServletRequest request) {
Object myObject=new Object();
request.setAttribute("myObject",myObject);
return "forward:/secondMapping";
}
you can also use ModelandView to carry object from method 1 to 2.
I have a List of Managers that I need to return in my #Controller method. I also have a User form view that I need to return simultaneously. managerList is returned from a previous #Controller. I may have been staring at this screen to long, it may not even make sense to do so, but can this be done?
#RequestMapping(value = "/getuserForm", produces = "text/html", method = RequestMethod.GET)
public ModelAndView returnUserForm(
#ModelAttribute("managerList") List<Manager> managerList,
Model model) {
//how to include managerList
return new ModelAndView("userForm");
}
Output would be a blank user form with a List of managers that say would be loaded into a select input. Any ideas?
Thanks much
You can use use public ModelAndView(String viewName, Map<String, ?> model).In model you can put your list.
You can use the model map of the ModelAndView Object
try the below code
#RequestMapping(value = "/getuserForm", produces = "text/html", method = RequestMethod.GET)
public ModelAndView returnUserForm(
#ModelAttribute("managerList") List<Manager> managerList,
Model model) {
//how to include managerList
ModelAndView mnv= new ModelAndView("userForm");
mnv.getModelMap().addAttribute("managerList", managerList);
return mnv;
}
#RequestMapping(value = "/getuserForm", produces = "text/html", method = RequestMethod.GET)
public ModelAndView returnUserForm(
#ModelAttribute("managerList") List<Manager> managerList,
Model model) {
//how to include managerList
model.addObject("managerList", managerList);
ModelAndView mnv= new ModelAndView("userForm");
mnv.getModelMap().addAttribute("managerList", managerList);
return mnv;
}
i am new Spring learner.i'm really confused about what is the difference between two concept:
#ModelAttribute
model.addAttribute
in below there are two "user" value.Are these same thing?Why should I use like this?
Thank you all
#RequestMapping(method = RequestMethod.GET)
public String setupForm(ModelMap model) {
model.addAttribute("user", new User());
return "editUser";
}
#RequestMapping(method = RequestMethod.POST)
public String processSubmit( #ModelAttribute("user") User user, BindingResult result, SessionStatus status) {
userStorageDao.save(user);
status.setComplete();
return "redirect:users.htm";
}
When used on an argument, #ModelAttribute behaves as follows:
An #ModelAttribute on a method argument indicates the argument should be retrieved from the model. If not present in the model, the argument should be instantiated first and then added to the model. Once present in the model, the argument’s fields should be populated from all request parameters that have matching names. This is known as data binding in Spring MVC, a very useful mechanism that saves you from having to parse each form field individually.
http://docs.spring.io/spring/docs/4.1.0.BUILD-SNAPSHOT/spring-framework-reference/htmlsingle/#mvc-ann-modelattrib-method-args
That's a very powerful feature. In your example, the User object is populated from the POST request automatically by Spring.
The first method, however, simply creates an instance of Userand adds it to the Model. It could be written like that to benefit from #ModelAttribute:
#RequestMapping(method = RequestMethod.GET)
public String setupForm(#ModelAttribute User user) {
// user.set...
return "editUser";
}
In order to access the redirect attributes in the redirected method, we utilize the model's map, like this :
#Controller
#RequestMapping("/foo")
public class FooController {
#RequestMapping(value = "/bar", method = RequestMethod.GET)
public ModelAndView handleGet(Model map) {
String some = (String) map.asMap().get("some");
}
#RequestMapping(value = "/bar", method = RequestMethod.POST)
public ModelAndView handlePost(RedirectAttributes redirectAttrs) {
redirectAttrs.addFlashAttributes("some", "thing");
return new ModelAndView().setViewName("redirect:/foo/bar");
}
}
But, why can't we access them in this way :
#RequestMapping(value = "/bar", method = RequestMethod.GET)
public ModelAndView handleGet(RedirectAttributes redAttr) {
String some = redAttr.getFlashAttributes().get("some");
}
If the only purpose of adding flashAttributes is that they become available to the model in the redirected method, what's the purpose of getFlashAttributes() ?
RedirectAttributes are for setting flash attributes before redirection. They are merged into model after the redirection so there is no reason to access them again via RedirectAttributes again as you have suggested.
Being able to work with the attributes just like with a map might be useful. You can check what have you set (containsKey, isEmpty, ...). However the use of the wildcard generic parameter Map<String, ?> getFlashAttributes() prevents writing into map and it is strange why they have used it instead of a plain Object parameter.
I am trying to retrieve some JSON data in my javascript by making a call to the controller. The controller returns a MappingJacksonJsonView ModelandView, but the .getJSON is always reporting a 404 at .../handhygiene.json.
Is there a problem with the way I am returning the ModelandView from the controller?
Controller
#RequestMapping(value = "/{room}/handhygiene.json", method = RequestMethod.GET)
public ModelAndView getHandHygienePageAsync(
#PathVariable(value = "room") String roomCode) {
ModelAndView mav = new ModelAndView(new MappingJacksonJsonView());
mav.getModelMap().addAttribute(blahblahblah); //adds some attributes
...
return mav;
}
Javascript
var currentURL = window.location;
$.getJSON(currentURL + ".json",
function(data) {
... //does stuff with data
}
If you're trying to get only an JSON object from Ajax request, you need to add #ResponseBody to your method, and make you result object as return from your method.
The #ResponseBody tells to Spring that he need to serialize your object to return to the client as content-type. By default, Spring uses JSON Serialization. ModelAndView will try to return an .JSP page. Maybe you don't have this jsp page on your resources so, the server return 404 error.
I Think this code should work for you:
#RequestMapping(value = "/{room}/handhygiene.json", method = RequestMethod.GET)
public #ResponseBody Room getHandHygienePageAsync(#PathVariable(value = "room") String roomCode) {
Room room = myService.findRoomByRoomCode(roomCode);
return room;
}
I'm assuming you're using the Room as your result object, but it may be another object or ArrayList, for example.
You cant take a look here for Spring example, and here for example and configuration.