How to display properties of specific object selected via dropdown? - spring-mvc

Question

I wrote a query in which I get the semester class, display its values ​​as a name and get its id. Accordingly, when I select the semester I need in the drop-down list, I am given the semester that I chose. But I also need to display its duration in another field, I can do this if I create a ForEach loop and use it to extract this value, but it displays absolutely all the available values, and not the one I need. Tell me how to do it right? For display I use Spring MVC. Now the page looks like this:
I am also attaching the jsp content:
<form:form action="allSemestrsSem" method="get" id="selectSemestr" modelAttribute="semestr">
<tr>
<td style="font-size: large;">Select semester</td>
<td style="padding-left: 50px">
<select name="selectSemestr">
<c:forEach items="${semestr}" var="semestr">
<option value="${semestr.id}">${semestr.name}</option>
</c:forEach>
</select>
</td>
<td style="padding-left: 20px">
<security:authorize access="hasRole('ADMIN')">
<input type="submit" id="button" value="select" /></td>
</security:authorize>
</tr>
<tr height="80px" style="font-size: large; font-weight: bold;">
<td colspan="3">Semester duration:
<c:forEach items="${semestr}" var="semestr"> ${semestr.duration} </c:forEach>
</td>
</tr>
</form:form>
And just in case my controller is:
#RequestMapping(value = "/allSemestrsSem", method = RequestMethod.GET)
public String allSemestrs(#RequestParam(name = "selectSemestr") String selectSemestr, Model model) {
List<Semestr> semestr = service.getSemestr();
model.addAttribute("semestr", semestr);
List<Discipline> allDisciplines = service.getDisciplineSemestrId(Integer.valueOf(selectSemestr));
model.addAttribute("allDisc", allDisciplines);
return "semestr";
}