grails select is not rendering value - grails

Question

I want to make a select box in grails. I am using 2.1.0. I have a view page which shows a select box named class. But it does not shows any value. The list I have used in the from attribute of select works fine is browser when I render it as json. Can anyone make my combo box work for me please ? Here is my code below :
my view page >>>
<g:form controller="admistratorAction" action="addStudent">
<table class="centerTable">
<div class="height"></div>
<tr>
<td><label>Full Name :</label></td>
<td><g:textField name="fullname" id="fullname" class="field"/></td>
</tr>
<tr>
<td> <label>Admission Class :</label></td>
<td><g:select name="class" id="class" class="field" from="${classList}" noSelection="['':'-Choose a class-']"/></td>
</tr>
<td colspan="2" align="right"><g:submitButton name="createSubmit" value="Create" class="button" onclick="return confirm('Are you sure???')"/></td>
</tr>
</table>
</g:form>
here is my controller >>
package administrator
import common.classes.Classes
import grails.converters.JSON
class AdmistratorActionController {
def addStudent = {
render "add student"
}
def classList = {
def classes = Classes.executeQuery("SELECT c.classes FROM Classes c")
def all_class = [classes : classes]
render all_class as JSON
}
}

Answer 1

You do not need to convert it to JSON in order to have it in gsp page
class AdmistratorActionController {
def addStudent = {
def n = params.fullName
def c = params.class
// do something with them
}
def classList = {
def classes = Classes.list()
// pass details to view 'classList'
[classList : classes]
}
}
Create -> views/administratorAction/classList.gsp
have you form ready and you will be able to get ${classList} in it