Question

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.

Answer 1

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.
• The addAttribute methods all return the ModelMap, so you can chain method called together, e.g. modelMap.addAttribute('x', x).addAttribute('y',y)
• The addAttribute methods checks that the values aren’t null
• The generic type of ModelMap 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.