Record the reason for this error
If you want to use the put request method, remember to use th:action in the form instead of th:href
If you use the post request method, th:href can also be successful,
So in the future, the form will use action in a unified way.
Incorrect
<form th:href="@{/employee}" method="post">correct
<form th:action="@{/employee}" method="post">