Thymeleaf template parsing error
May be you are missing a closing tag somewhere. I have no idea what you have in the HTML template, unless you post the complete code.
But replace your current file with this template. And it should work. Then you can add your missing codes to it.
<!DOCTYPE html>
<html xmlns:th="http://www.thymeleaf.org">
<head lang="en"></head>
<body>
<tr th:each="customer : ${customers}">
<td th:text="${customer.identity}">001</td>
<td th:text="${customer.name}">Name</td>
<td th:text="${customer.address}">Address</td>
<td th:text="${customer.age}">Age</td>
</tr>
</body>
</html>