@GetMapping("/register")
    public String registerPage(Model model) {
    	 model.addAttribute("user", new UserDto());
        return "registration"; // This corresponds to registration.html in templates folder
    }
    
    @PostMapping("/registrationPage")
    public String registerUser(@ModelAttribute("user") UserDto dto) {
    	UserDetails details = User.builder().username(dto.getName()).
    			password(new BCryptPasswordEncoder()
    					.encode(dto.getPassword()))
    			.roles("ROLE_USER").build();
    	
    	repository.saveUser(details);
    	
        return "success"; // This corresponds to success.html in templates folder (if you have one)
    }
    
    package com.ShelfSpace.ShelfSpace.model;

public class UserDto {

	private String name;
	private String email;
	private String password;

	// Getters and Setters
	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public String getEmail() {
		return email;
	}

	public void setEmail(String email) {
		this.email = email;
	}

	public String getPassword() {
		return password;
	}

	public void setPassword(String password) {
		this.password = password;
	}
}

package com.ShelfSpace.ShelfSpace.model;


import java.util.List;

import jakarta.persistence.Column;
import jakarta.persistence.Entity;
import jakarta.persistence.GeneratedValue;
import jakarta.persistence.GenerationType;
import jakarta.persistence.Id;
import jakarta.persistence.ManyToMany;
import jakarta.persistence.Table;
import lombok.Data;

@Entity
@Data
@Table(name = "shelfspace_user_role")
public class UserRoleEntity {

	@Id
	@Column(name = "user_role_id")
	 @GeneratedValue(strategy = GenerationType.IDENTITY)
	private long roleId;
	
	@Column(name = "user_role")
	private String roleName;
	
	@Column(name = "user_role_id")
	@ManyToMany(mappedBy = "roles")
	private List<UserEntity>users;
}

package com.ShelfSpace.ShelfSpace.repository;

import java.util.Optional;

import org.springframework.data.repository.CrudRepository;
import org.springframework.security.core.userdetails.UserDetails;
import org.springframework.stereotype.Repository;

import com.ShelfSpace.ShelfSpace.model.UserDto;
import com.ShelfSpace.ShelfSpace.model.UserEntity;

@Repository
public interface UserRepository extends CrudRepository<UserEntity, Long> {
    Optional<UserDto> findUserByEmail(String email);
    void saveUser(UserDetails userDetails);
}

package com.ShelfSpace.ShelfSpace.service;

import org.springframework.security.core.userdetails.UserDetails;
import org.springframework.security.core.userdetails.UserDetailsService;
import org.springframework.security.core.userdetails.UsernameNotFoundException;

public class UserService implements UserDetailsService {

	@Override
	public UserDetails loadUserByUsername(String username) throws UsernameNotFoundException {
		// TODO Auto-generated method stub
		return null;
	}
}