how to get the selected value to input text box in thymeleaf

Question

Onchange in the dropdown, dist_nm should be reflected in the text box.. Can someone help?

<select id="editDistName" th:field="*{districts}" th:onchange="selectedDistName();">
    <option value="default">Select the District </option>
    <option th:each="dist : ${districts}" th:value="${dist.dist_id}" 
            th:text="${dist.dist_nm}" th:selected="${dist.dist_nm}"/>
</select>
<input type="text" class="form-control" id="dist_nm" name="dist_nm"/>

Answer 1

Finally, I found a way to fetch the name through table by passing ID from Dropdown.

HTML - form

<div class="form-group">
        <select id='DCode' name='DCode'>
             <option th:each="dist : ${districts}"
                 th:value="${dist.dist_id}"
                 th:text="${dropDownItem.dist_nm}" />
         </select>
    </div>
    <div class="form-group">
        <div id="textBox"></div>
    </div>

Repository -- fetching name through ID

@Query("SELECT name FROM Sample WHERE id =:ID ORDER BY id")     
public String getName(@Param("ID") int code);

AjaxController

@RequestMapping(value="Ajax",method={ RequestMethod.GET, RequestMethod.POST })
public @ResponseBody String editName(@RequestParam(value="ID") int d_Code ) {
    String name = rep.getName(d_Code);
    return name;
}

JS-file /passing ID to get Name from table/

$(document).on("change", "#DCode", function() {
    try {
        var d_id= $("#DCode option:selected").val();
        var params = {ID : d_id};
        $.ajax({
            type:'POST',
            url:'/Ajax',
            data:params,
            success:function(responseJson){
                var jSON_res = JSON.stringify(responseJson);
                var d_Name = jSON_res.replace(/\"/g, "" ); //remove double quote from string 
                var text_val = "<input type='text' id ='new_name' name ='new_name' " +
                            " value =' "+d_Name+" ' />";
                $("#textBox").empty().append(text_val);
            }//success function
        });     
    } catch(err) {
        alert("Exception  ::-- "+err);
    }   
});

I'm very new to spring boot and this is one of the way I tried. Let me know, if there is better way of getting the result. Thank you,