i have just started spring boot so i might be making silly mistakes.I am making a regiser.html page which is linked to login page after entering username id and password in register page when we click on submit button it takes us to login page and the data we store will be stored in register table of Mysql.
In login page when we enter the username and password it will check weather this username and password is present in register table of mysql.
If it is present then it will take us to chatpage were we can enter the data and on clicking on submit button it will get stored in the storechat table of the mysql. And if the username and password is not present in the register table of the mysql then it will show that user is not present in the login page itself.
i am getting this error:
Prediction Mode AltAndCOntextMap[JavaApplication]C:/Program FIlesjavajdk -17binjavaw.exe
this is my MyService.java code.

package com.example.chatdemo.Service;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import com.example.chatdemo.Entity.Exwhich;
import com.example.chatdemo.Repository.Checkdata;

@Service
public class MyService {
    @Autowired
    private Checkdata checkdata1;
    public boolean checkexist(String newuser,String newpass) {
        Exwhich exwhich= checkdata1.samemethod(newuser,newpass);
        return exwhich!= null;
    
    }
    
}

this is my repository (Registerrepo.java) code:

package com.example.chatdemo.Repository;

import org.springframework.data.jpa.repository.JpaRepository;

import com.example.chatdemo.Entity.EntityClass;


public interface Registerrepo  extends JpaRepository<EntityClass,String> {

}

this is my another repository named checkdata.java

package com.example.chatdemo.Repository;

import org.springframework.data.jpa.repository.JpaRepository;

import com.example.chatdemo.Entity.Exwhich;

public interface Checkdata extends JpaRepository<Exwhich,Long> {
    
    Exwhich samemethod( String newuser, String newpass);
  }

this is my controller file named Controller1.java

package com.example.chatdemo.Controller;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

import com.example.chatdemo.Entity.EntityClass;
import com.example.chatdemo.Repository.Registerrepo;
import com.example.chatdemo.Service.MyService;

import jakarta.persistence.Entity;
@RestController
public class Controller1 {
    @Autowired
    private Registerrepo reopo;

    @GetMapping("/showchatpage")
    public String getnewdata() {
        return "register";
    }
    @PostMapping("/submit")
    public String storedatabase(@ModelAttribute EntityClass E)
    {
        reopo.save(E);
        return "abcd";
    }
    @Controller
    public class LoginController{
        @Autowired
        private MyService mynewservice;
    
        
        @PostMapping("/login")
        public String login(@RequestParam("mynewuser") String newuser,
        @RequestParam("newpass") String newpass, Model model) {

            boolean number=mynewservice.checkexist(newuser,newpass);
            if(number) {
                return "redirect:/showchatpage";
            }
            else {
                model.addAttribute("message","user dont exist");
                return "login";
            }
        }
    }
}

this is my Entity class named EntityClass.java

package com.example.chatdemo.Entity;

import jakarta.persistence.Entity;
import jakarta.persistence.Id;
import jakarta.persistence.Table;

@Entity
@Table(name="register")
public class EntityClass {
    @Id
    String name;
    String password;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getPassword() {
        return password;
    }
    public void setPassword(String password) {
        this.password = password;
    }
    @Override
    public String toString() {
        return "Entity [name=" + name + ", password=" + password + "]";
    }

}

this is my another Entity class names Exwhich.java

package com.example.chatdemo.Entity;

public class Exwhich {
   
}

i am getting no error inside code just getting error on running code.