ECサイトの管理者としてログインするとエラーが発生してしまいます。

前提・実現したいこと

ECサイトの管理者サイトの開発の演習中ですが、確認のためにURLタブから開いてみると、ログイン後にエラーが起きて画面が表示されません。エラーの原因とエラーの解決方法を教えてもらえると助かります。

発生している問題・エラーメッセージ

Whitelabel Error Page
This application has no explicit mapping for /error, so you are seeing this as a fallback.

該当のソースコード

java
1package jp.co.internous.ecsite.controller;
2
3import java.util.List;
4
5import org.springframework.beans.factory.annotation.Autowired;
6import org.springframework.stereotype.Controller;
7import org.springframework.ui.Model;
8import org.springframework.web.bind.annotation.PostMapping;
9import org.springframework.web.bind.annotation.RequestMapping;
10
11
12import jp.co.internous.ecsite.model.dao.GoodsRepository;
13import jp.co.internous.ecsite.model.dao.UserRepository;
14import jp.co.internous.ecsite.model.entity.Goods;
15import jp.co.internous.ecsite.model.entity.User;
16import jp.co.internous.ecsite.model.form.LoginForm;
17
18@Controller
19@RequestMapping("/ecsite/admin")
20public class AdminController {
21	
22	@Autowired
23	private UserRepository userRepos;
24	
25	@Autowired
26	private GoodsRepository goodsRepos;
27
28	@RequestMapping("/")
29	public String index() {
30		return "adminindex";
31	}
32	
33	@PostMapping("/welcome")
34	public String welcome(LoginForm form, Model m) {
35		List<User> users = userRepos.findByUserNameAndPassword(form.getUserName(), form.getPassword());
36		
37		if(users != null && users.size() > 0) {
38			boolean isAdmin = users.get(0).getIsAdmin() != 0;
39			if(isAdmin) {
40				List<Goods>goods = goodsRepos.findAll();
41				m.addAttribute("userName", users.get(0).getUserName());
42				m.addAttribute("password", users.get(0).getPassword());
43				m.addAttribute("goods", goods);
44			}
45		}
46		
47		return "welcome";
48	}
49}
50

html
1<!DOCTYPE html>
2<html xmlns:th="http://www.thymeleaf.org">
3<head>
4<meta charset="UTF-8" />
5<link href="/css/style.css" th:href="@{/css/style.css}" rel="stylesheet" />
6<title>ECサイト</title>
7</head>
8<body>
9
10<header>
11	<h1>My EC Site -- Admin page</h1>
12</header>
13
14<div id="adminPage">
15	<h2>管理者ログイン</h2>
16	<form name="loginForm" method ="post" action="/ecsite/admin/welcome" th:action="@{/ecsite/admin/welcome}">
17		<p>User name:<input type="text" name="userName" /></p>
18		<p>Password :<input type="password" name="password" /></p>
19		<button type="submit">Login</button>
20	</form>
21</div>
22
23</body>
24</html>

java
1package jp.co.internous.ecsite.model.form;
2
3import java.io.Serializable;
4
5public class LoginForm implements Serializable{
6	private static final long serialVersionUID = 1L;
7	
8	private String userName;
9	private String password;
10	
11	public String getUserName() {
12		return userName;
13	}
14	
15	public void setUserName(String userName) {
16		this.userName = userName;
17	}
18	
19	public String getPassword() {
20		return password;
21	}
22	public void setPassword(String password) {
23		this.password = password;
24	}
25	
26
27}
28

html
1<!DOCTYPE html>
2<html xmlns:th="http://www.thymeleaf.org">
3<head>
4<meta charset="UTF-8" />
5<link href="/css/style.css" th:href="@{/css/style.css}" rel="stylesheet" />
6<title>ECサイト</title>
7</head>
8<body>
9
10<header>
11	<h1>My EC Site</h1>
12</header>
13
14<table id="adminTable">
15	<thead>
16		<tr>
17			<th>ID</th><th>商品名	</th><th>価格</th><th>削除</th>
18		</tr>
19	</thead>
20<tbody>
21	<tr th:each=“item: ${goods}”>
22		<td th:text=“${item.id}” />
23		<td th:text=“${item.goodsName}” />
24		<td th:text=“${item.price}” />
25		<td><button type=“submit” class=“deleteBtn”>削除</button></td>
26	</tr>
27
28</tbody>
29</table>
30<form name="goodsForm" id="adminPage" method="post" action="/ecsite/admin/goodsMst" th:action="@{/ecsite/admin/goodsMst}">
31	<button type="submit" th:if="${userName != null}">新規追加</button>
32	<input type="hidden" name="userName" th:value="${userName}" />
33	<input type="hidden" name="password" th:value="${password}" />
34	</form>
35
36</body>
37</html>

java
1package jp.co.internous.ecsite.model.dao;
2
3import java.util.List;
4
5import org.springframework.data.jpa.repository.JpaRepository;
6
7import jp.co.internous.ecsite.model.entity.User;
8
9public interface UserRepository extends JpaRepository<User, Long>{
10
11	List<User> findByUserNameAndPassword(String userName, String password);
12}
13

java
1package jp.co.internous.ecsite.model.dao;
2
3import org.springframework.data.jpa.repository.JpaRepository;
4
5import jp.co.internous.ecsite.model.entity.Goods;
6
7public interface GoodsRepository extends JpaRepository<Goods, Long>{
8
9}
10