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What are the benifits of using ModelMap instead of a simple Map in Spring MVC. I see in the code implementation that they put the datatype of the attribute added in the map as key instead to be made available on the form.
Can anyone explain with an example.
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Model is an interface while ModelMap is a class. ModelAndView is just a container for both a ModelMap and a view object. It allows a controller to return both as a single value.
ModelAndView is a holder for both Model and View in the web MVC framework. These two classes are distinct; ModelAndView merely holds both to make it possible for a controller to return both model and view in a single return value. The view is resolved by a ViewResolver object; the model is data stored in a Map .
I always use the approach where controller methods return ModelAndView . Simply because it tends to make the controller methods a little more terse. The method parameters are now strictly input parameters. And all output related data is contained in the object returned from the method.
ModelMap subclasses LinkedHashMap, and provides some additional conveniences to make it a bit easier to use by controllers
addAttribute can be called with just a value, and the map key is then inferred from the type. addAttribute methods all return the ModelMap, so you can chain method called together, e.g. modelMap.addAttribute('x', x).addAttribute('y',y) addAttribute methods checks that the values aren't nullModelMap is fixed at Map<String, Object>, which is the only one that makes sense for a view model.So nothing earth-shattering, but enough to make it a bit nicer than a raw Map. Spring will let you use either one.
You can also use the Model interface, which provides nothing other than the addAttribute methods, and is implemented by the ExtendedModelMap class which itself adds further conveniences.
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