Model

You can use the @ModelAttribute annotation:

• As a method argument in methods with the @RequestMapping annotation to create or access an object from the model and bind it to a request via WebDataBinder.

• As a method-level annotation in classes marked with @Controller or @ControllerAdvice annotations that helps initialize the model before calling a method with the @RequestMapping annotation.

• For the @RequestMapping method to indicate that its return value is a model attribute.

This section covers methods, the @ModelAttribute annotation is the second item in the previous list. A controller can have any number of methods marked with the @ModelAttribute annotation. All such methods are called before methods with the @RequestMapping annotation in the same controller. A method annotated with @ModelAttribute can also be shared between controllers via the @ControllerAdvice annotation.

Methods with the @ModelAttribute annotation have flexible method signatures. They support many of the same arguments as methods marked with the @RequestMapping annotation, except for the @ModelAttribute annotation itself or anything associated with the request body.

The following example shows a method annotated with @ModelAttribute:

@ModelAttribute
public void populateModel(@RequestParam String number, Model model) {
    model.addAttribute(accountRepository.findAccount(number));
    // add more...
}

@ModelAttribute
fun populateModel(@RequestParam number: String, model: Model) {
    model.addAttribute(accountRepository.findAccount(number))
    // add more...
}

The following example adds only one attribute:

@ModelAttribute
public Account addAccount(@RequestParam String number) {
    return accountRepository.findAccount(number);
}

@ModelAttribute
fun addAccount(@RequestParam number: String): Account {
    return accountRepository.findAccount(number)
}

You can also use the @ModelAttribute annotation as a method-level annotation for methods annotated with @RequestMapping, in which case the return value of the method annotated with @RequestMapping will be interpreted as a model attribute. This is usually not required as it is the default operating logic in HTML controllers, unless the return value is a String, which would otherwise be interpreted as the name of the view. The @ModelAttribute annotation can also customize the model attribute name, as shown in the following example:

@GetMapping("/accounts/{id}")
@ModelAttribute("myAccount")
public Account handle() {
    // ...
    return account;
}

@GetMapping("/accounts/{id}")
@ModelAttribute("myAccount")
fun handle(): Account {
    // ...
    return account
}