Check out example codes for "how to set a default value for a dropdownlist in html with thymeleaf spring". It will help you in understanding the concepts better.

Code Example 1

<label for="drink">Drink</label>
    <select id="drink" name="drink">
        <option th:each="drink : ${drinks}" th:text="${}"                //drinks are an array of ENUMs here, are the lowercase equivalent
                th:value="${drink}" th:selected=${drink==customer.drink}></option> //the customer's last drink will be the default

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