댓글기능2 CommentController 오류

CommentController 클래스에서 코드를 이렇게 작성했고,

package com.jaeyeong.sbmall.comment;

import com.jaeyeong.sbmall.member.CustomUser;
import lombok.RequiredArgsConstructor;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.security.core.Authentication;

@Controller
@RequiredArgsConstructor
public class CommentController<CustomUser> {

  private final CommentRepository commentRepository;

@PostMapping("/comment")
  String postComment(@RequestParam String content, @RequestParam Long parent, Authentication auth) {
    CustomUser user = (CustomUser) auth.getPrincipal();
    var data = new Comment();
    data.setContent(content);
    data.setUsername(user.getUsername());   // 이 부분에서 오류남
    data.setParentId(parent);
    commentRepository.save(data);
    return "redirect:/list";
  }
}



CustomUser 클래스도 따로 아래와 같이 분리했는데

package com.jaeyeong.sbmall.member;

import org.springframework.security.core.GrantedAuthority;
import org.springframework.security.core.userdetails.User;

import java.util.Collection;

public class CustomUser extends User {
  public String displayName;
  public CustomUser(
      String username,
      String password,
      Collection<? extends GrantedAuthority> authorities
  ) {
    super(username, password, authorities);
  }
}


자꾸 CommentController.java의 'data.setUsername(user.getUsername());' 부분에서 'Cannot resolve method 'getUsername' in 'CustomUser''라는 오류가 발생합니다.