코드

package com.sparta.springassignment1.controller;

import com.sparta.springassignment1.dto.ClientDTO;
import com.sparta.springassignment1.entity.Client;
import com.sparta.springassignment1.service.ClientService;
import lombok.RequiredArgsConstructor;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.*;

@Controller
@RequiredArgsConstructor
public class ClientController {

private final ClientService clientService;

@GetMapping("/")
public String index() {

    return "index";
}

@GetMapping("/api/blog/view/{id}")
public String blogPostView(Model model, @PathVariable Long id) {
    model.addAttribute("client", clientService.getClientPostByid(id).get());
    return "view";
}

@PostMapping("/api/blog/write")
public String createMemo(@RequestBody ClientDTO clientDTO) {
    clientService.createPost(clientDTO);
    return "redirect:/api/blog/list";
}

@GetMapping("/api/blog/write")
public String blogPostWrite() {

    return "write";
}

@GetMapping("/api/blog/list")
public String getPost(Model model) {
    model.addAttribute("client", clientService.getAllPost());
    return "list";
}

@GetMapping("/api/blog/update/{id}")
public String updatePro(@PathVariable("id") Long id, Model model, String password) {
    Client client = clientService.getClientPostByid(id).get();

// if (clientService.getClientPassWord(password)) {

        ClientDTO clientDTO = new ClientDTO();
        clientDTO.setUsername(client.getUsername());
        clientDTO.setTitle(client.getTitle());
        clientDTO.setContent(client.getContent());

        model.addAttribute("clientDTO", clientDTO);
    return "edit";

}

// }

@PostMapping("/api/blog/delete/{id}")
public String deleteById(@PathVariable("id") Long id, @RequestParam("password") String password, Model model) {
    boolean deleteCheckFlag = clientService.deletePost(id, password);
    if (!deleteCheckFlag) {
        model.addAttribute("message", "비밀번호가 일치하지 않습니다.");
        return "redirect:/api/blog/postDelete";
    }
    model.addAttribute("message", "게시글 삭제가 성공하였습니다.");
    return "redirect:/api/blog/list";
}

@GetMapping("/api/blog/delete/{id}")
public String deletePrepared(@PathVariable("id") Long id, Model model) {
    model.addAttribute("id", id);
    return "postDelete";
}

}