ComboBox store from remote data

If remote data like :

[{"createDate":"2009-12-04T00:38:38","createUserID":
"System","param_Description":"??","param_Group_Name":
"Locale","param_Name":"EnUS","param_Sort_Order":1,
"param_Status":1,"param_Value":"en_US","serNo":
"PARAM00000000000000000003","updateDate":
"2009-12-04T00:38:41","updateUserID":"System"},
{"createDate":"2009-12-04T00:37:34","createUserID":
"System","param_Description":"??(??)",
"param_Group_Name":"Locale","param_Name":
"ZhTW","param_Sort_Order":0,"param_Status":1,
"param_Value":"zh_TW","serNo":"PARAM00000000000000000002",
"updateDate":"2009-12-04T00:37:55","updateUserID":"System"}]

Step1. New JsonReader object like :

var localeJsonDefine = new Ext.data.JsonReader({}, 
   ['param_Group_Name', 'param_Name', 'param_Value', 'param_Description']);

Step2. New data Store like :

var localeDataStore = new Ext.data.Store({
      proxy : new Ext.data.HttpProxy({
         url : 'http://localhost:6957/SLPortal/getLocaleGroupAction.action' 
      }),
      reader : localeJsonDefine,
      remoteSort : false
   });

Step3. New ComboBox like :

var localeCbx = new Ext.form.ComboBox({
      fieldLabel : localeFieldText,
      store : localeDataStore, 
      editable : false,
      emptyText : localeFieldEmptyText, 
      valueField : 'param_Value',
      displayField : 'param_Description',
      mode : 'remote',
      triggerAction : 'all'
   });