Thymeleaf Property or field 'xxxx' cannot be found on null

Error: Property or field 'headUrl' cannot be found on null.

But I can't find null.I check my code ,still have no idea.

The result was there should be 10 news,other 9 news was normal ,the last has error,can't show show the URL correctly.

Here is the code(I don't know how to paste picture):

Home.html:

<div class="user-avatar"> <a href="/user/${vo.user.id}"> <img width="32" class="img-circle" th:src="${vo.user.headUrl}"> </a> </div> 

Class User:

private String headUrl; public User() {} public User(String name) { this.name = name; this.password = ""; this.salt = ""; this.headUrl = ""; } public String getHeadUrl() { return headUrl; } public void setHeadUrl(String headUrl) { this.headUrl = headUrl; } 

Database:

@Test public void contextLoads() { Random random = new Random(); for (int i = 1; i < 10; i++) { User user = new User(); user.setHeadUrl(String.format("http://images.nowcoder.com/head/%dt.png", random.nextInt(100))); user.setName(String.format("USER%d", i)); user.setPassword(String.format("PASSWORD--%d",i*i)); user.setSalt(String.format("SALT %d HelloWorld",i*5+20)); userDao.addUser(user); } } 

Main:

@RequestMapping(path = {"/", "/index"}, method = {RequestMethod.GET,RequestMethod.POST}) public String index(Model model){ List<News> newsList = newsService.getLatesNews(0, 0,10); List<Map> vos = new ArrayList<>(); for(News news :newsList){ Map<String, Object> vo = new HashMap<String, Object>(); vo.put("news",news); vo.put("user", userService.getUser(news.getUserId())); vos.add(vo); } model.addAttribute("vos", vos); return "home.html"; } 

Class UserService:

public class UserService { @Autowired private UserDao userDao; public User getUser(int id) return userDao.selectById(id);}