Question

I have a method in my AccountController like

 @RequestMapping(method = { RequestMethod.POST, RequestMethod.PUT })
    public String update(@ModelAttribute Account account) {
this.getAccountDao().save(account);
return "redirect:/users/account/";
}

I am using org.springframework.web.filter.HiddenHttpMethodFilter and so my view has a hidden form field as –

<form:form method="POST" modelAttribute="account">
      <input type="hidden" name="_method" value="PUT" />
....

Now my question is how does the controller know when to Create a new Account or to Update it or how does it know if the request is a POST or a PUT? To me it always looks like it is going to be PUT.

I just don’t like using anything apart from GET and POST. The controller does not need to care whether it needs to create a new one or update it. If the form has a hidden account id field, the service can figure out what DAO method to call.

EDIT
If this is only going to be a PUT request then I would need to create a new jsp for POST. Unfortunately both requests are very similar in that they need almost exact data to be submitted, except for account id. I want to be able to use this same method from the controller and the same jsp for both POST and PUT and depending on either the model – account is saved or updated.

Answer 1

The controller doesn’t know if you create or update an entity, it only knows the RequestMethods which the method reacts to.

The hidden field you specified and the HiddenHttpMethodFilter you are using, result in PUT being the HTTP method, visible to your controller, as the filter changes the method in the request. (according to the javadocs).

In result, the browser uses POST to transmit its data to the server, then the Filter runs and changes the method in the request to PUT, so for the application behind that Filter it looks like the request had been sent with PUT.

I don’t see a problem in being very similar code, just factor the similar behavoir out to another method.. eg:

@RequestMapping(method = { RequestMethod.POST})
public String update(@ModelAttribute Account account) {
     // do POST specific things..

      // and common operations
      commonOperation();
}

@RequestMapping(method = { RequestMethod.PUT })
public String updateWithPut(@ModelAttribute Account account) {
      // do PUT specific things...

      // and common operations
      commonOperation();
}

// code that put and post methods have in common
private void commonOperation() {
 // a lot of common code
 // that needs to be done
}