Have multiple method=RequestMethod.POST in controller and how to call each of them?

In my spring controller, I have three functions

@Controller
public class Controll {

    @RequestMapping(value="/signup",method=RequestMethod.GET)
    public String signup(@ModelAttribute("signuper") Signuper signuper, ModelMap model){

        if(signuper.getSignupFName()!=null){  
            //dosomething
            return "emailForm";              
        }
      
        //dosomething
        return "signupForm";
    }

    @RequestMapping(value="/signup",method=RequestMethod.POST)
	public String signup(@Valid Signuper signuper,BindingResult result, ModelMap model,
        RedirectAttributes attributes)
	{
        //dosomething
        attributes.addFlashAttribute("signuper",signuper);
		return "redirect:signup";
    }

    @RequestMapping(value="/signup",method=RequestMethod.POST, params = "email")
	public String signupE(@Valid EmailVerify emailVerify,BindingResult result,ModelMap model) {
        //dosomething
     	return "signupSuccess";
	}
}

The user goes to /signup in the web browser.
Method(signup with method = GET) gets called.
User fills out "signupForm" and the info goes to Method(signup with method = POST).
Method(signup with method = POST) does validation and if everything is good, it redirects back to Method(signup with method = GET) with Signuper info. Becuase signuper.getSignupFName() will not be null now, user will have to fill "emailForm".

How do I go to Method(signupE with method = POST)?

MAIN QUESTIONS TO ANSWER (everything else was background info, but pls read it) :

1. How do you create a param in a method so that when it can pick which method = POST Method it can call?

2. How to have multiple method=RequestMethod.POST in controller and how to call each of them?

1. How do you create a param in a method so that when it can pick which method = POST Method it can call?

I suppose you want to call the method signupE once the user fills the "emailForm". So in the "emailForm", the form "action" URL would have to be attached with a request parameter. How you do that depends on what server side tech you have used for generating the HTML pages. It can be JSP/Thymeleaf etc. If you need help with that, specify which one you're using.

I can see that you've specified params = "email" in the RequestMapping, but you haven't specified any @RequestParam("email") in the method arguments. It should be specified like:

@RequestMapping(value="/signup",method=RequestMethod.POST, params = "email")
   public String signupE(@RequestParam("email") String email, @Valid EmailVerify emailVerify,BindingResult result,ModelMap model) {
       //dosomething
       return "signupSuccess";
   }

2. How to have multiple method=RequestMethod.POST in controller and how to call each of them?

One of the ways to do that is by differentiating them on the basis of request parameters, using the "params" attribute. Since you've already used that, I don't think I should explain how that works.