When is a @ModelAttribute annotated method called precisely?
data-binding, java, modelattribute, spring, spring-mvc
Solution
The `setupItem` is going to be called once per request to any of the `@RequestMapping` methods in this controller, right before the `@RequestMapping` method is called. So for your `addItem` method the flow will be - call the `setupItem`, creating a model attribute called `item`, since your `addItem` argument is also tagged with `@ModelAttribute`, the `item` is going to be enhanced with POST'ed parameters at this point.
Problem
The following is a simple Spring form controller to handle 'add item' user requests: ``` @Controller @RequestMapping("/addItem.htm") public class AddItemFormController { @Autowired ItemService itemService; @RequestMapping(method = RequestMethod.GET) public String setupForm(ModelMap model) { return "addItem"; } @ModelAttribute("item") public Item setupItem() { Item item = new Item(); return item; } @RequestMapping(method = RequestMethod.POST) protected String addItem(@ModelAttribute("item") Item item) { itemService.addItem(item); return "itemAdded"; } } ``` I read somewhere that: `(...) the @ModelAttribute is also pulling double duty by populating the model with a new instance of Item before the form is displayed and then pulling the Item from the model so that it can be given to addItem() for processing.` My question is, when and how often is `setupItem()` going to be called precisely? Will Spring keep a separate model copy if user requests multiple add item?