播放Frameowrk Null指针异常

Question

尝试从表单中获取数据时出现Null指针异常，我填写了表单并获得了名字。但是会抛出空指针异常。我正在使用play2.6

controllers / Register.java：

package controllers;
import models.SignUp;
import play.data.Form;
import play.data.FormFactory;
import play.mvc.Controller;
import play.mvc.Result;
import javax.inject.Inject;
public class Register extends Controller{
   @Inject
   FormFactory formFactory;
   public Result index(){
       Form<SignUp> signupform = formFactory.form(SignUp.class);
       return ok(views.html.index.render(signupform));
   }
   public Result submit(){
       Form<SignUp> signupform     =formFactory.form(SignUp.class).bindFromRequest();
       if(signupform.hasErrors()){
          flash("danger","Please Correct the Form Below");
           //send bad request error
       }
       SignUp details = signupform.get();
       return ok("Hello"+ details.firstName);
  }
}

模型/注册：

package models;

    import play.data.validation.Constraints;
    import javax.validation.constraints.Max;

    public class SignUp {
        public String firstName;
        public String lastName;
        public String emailId;
        public String password;
    }

@ views / index

@(signupform : Form[SignUp])
@import helper._
@main("SignUp") {
  <h1>SignUp Form</h1>
  @helper.form(action = helper.CSRF(routes.Register.submit())){
    @helper.inputText(signupform("firsName"),'class -> "form-control")
   @helper.inputText(signupform("lastName"),'class -> "form-control")
   @helper.inputText(signupform("emailId"),'class -> "form-control")
    @helper.inputPassword(signupform("password"),'class -> "form-control")
        <button type="submit">Submit<button>
   }
}