Request parameters not mapped to Model class in struts 2 using ModelDriven Interceptor

Question

When submitting form in JSP to struts 2 action class then ModelDriven Object is not being created properly. Only some of the fields are populated not others.

Below are the parameters submitted to the Action Class using post method :

orderDaysMap['10065A5023'].orderDayMap['100655023299912319901566237468850'].facility.vendor.vendorName: 
orderDaysMap['10065A5023'].orderDayMap['100655023299912319901566237468850'].facility.vendor.number: 10065
orderDaysMap['10065A5023'].orderDayMap['100655023299912319901566237468850'].facility.vendor.vendorDeptNumber: 0
orderDaysMap['10065A5023'].orderDayMap['100655023299912319901566237468850'].facility.masterVendor.vendorName: 10064
orderDaysMap['10065A5023'].orderDayMap['100655023299912319901566237468850'].facility.masterVendor.number: 
orderDaysMap['10065A5023'].orderDayMap['100655023299912319901566237468850'].facility.masterVendor.vendorDeptNumber: 
orderDaysMap['10065A5023'].orderDayMap['100655023299912319901566237468850'].facility.facility.facilityName: 
orderDaysMap['10065A5023'].orderDayMap['100655023299912319901566237468850'].facility.facility.facilityNumber: 5023
orderDaysMap['10065A5023'].orderDayMap['100655023299912319901566237468850'].facility.facility.facilityBUID: 
orderDaysMap['10065A5023'].orderDayMap['100655023299912319901566237468850'].facility.isValid: true

Model Object :

import java.util.Date;
import java.util.Map;
import java.util.TreeMap;
import java.util.logging.Logger;


public class OrderDaysForm {



    private Map<String, OrderDayDisplay> orderDaysMap = null;


    public Map<String, OrderDayDisplay> getOrderDaysMap() {
        return orderDaysMap;
    }
    public void setOrderDaysMap(Map<String, OrderDayDisplay> orderDaysMap) 
    {
        this.orderDaysMap = orderDaysMap;
    }


}

public class OrderDayDisplay implements Exportable, java.io.Serializable {
    private static final long serialVersionUID = 20070403092401L;

    private Map<String, OrderDayRecord> orderDayMap;

    public Map<String, OrderDayRecord> getOrderDayMap() {
        return orderDayMap;
    }
    public void setOrderDayMap(Map<String, OrderDayRecord> m) {
        this.orderDayMap = m;
    }



}

public class OrderDayRecord extends OrderDay implements Exportable {

    private static final long serialVersionUID = 20070403105701L;

}

public class OrderDay implements java.io.Serializable {

    private static final long serialVersionUID = 20070202142501L;
    private VendorFacility facility;

}

VendorFacility object corresponding to below request parameters is not populated in OrderDayRecord class :

orderDaysMap['10065A5023'].orderDayMap['100655023299912319901566237468850'].facility.facility.facilityName: 
orderDaysMap['10065A5023'].orderDayMap['100655023299912319901566237468850'].facility.facility.facilityNumber: 5023
orderDaysMap['10065A5023'].orderDayMap['100655023299912319901566237468850'].facility.facility.facilityBUID: