try{
            SessionFactory sessionFactory = new Configuration().setProperty("hibernate.show_sql", "true").configure("\\order_mod\\hibernate.cfg.xml").buildSessionFactory();
            session =sessionFactory.openSession();
            Transaction tx = session.beginTransaction();
            order.getOrderno(); //here orderNo is equal to 5
            session.saveOrUpdate(order);
           
        order.getOrderno(); //here orderNo is null
        order.getVendorname();

            tx.commit();
            System.out.println("Done");
        }catch(Exception e){
            System.out.println(e.getMessage().toString());
        }finally{
             session.flush();
            session.close();
        }

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://hibernate.sourceforge.net/hibernate-mapping-2.0.dtd" >
   
<hibernate-mapping>
<!--
    Created by the Middlegen Hibernate plugin 2.1

    http://boss.bekk.no/boss/middlegen/
    http://www.hibernate.org/
-->

<class
    name="order_mod.Onorder"
    table="ONORDER"
>

    <id
        name="autono"
        type="java.lang.Integer"
        column="AUTONO">
        <generator class="increment"/>
    </id>

    <property
        name="plu"
        type="java.lang.String"
        column="PLU"
        length="65"
    />
   
        <property
        name="orderno"
        type="java.lang.Integer"
        column="ORDERNO"
        length="10"
    />
   
    <property
        name="itemno"
        type="java.lang.String"
        column="ITEMNO"
        length="65"
    />
    <property
        name="locno"
        type="int"
        column="LOCNO"
        not-null="true"
        length="10"
    />
    <property
        name="description"
        type="java.lang.String"
        column="DESCRIPTION"
        not-null="true"
        length="255"
    />
    <property
        name="vendorno"
        type="java.lang.Integer"
        column="VENDORNO"
        length="10"
    />
    <property
        name="projectedcost"
        type="java.lang.Double"
        column="PROJECTEDCOST"
        length="15"
    />
    <property
        name="actualcost"
        type="java.lang.Double"
        column="ACTUALCOST"
        length="15"
    />
    <property
        name="dateordered"
        type="java.sql.Timestamp"
        column="DATEORDERED"
        length="19"
    />
    <property
        name="datereceived"
        type="java.sql.Timestamp"
        column="DATERECEIVED"
        length="19"
    />
    <property
        name="modified"
        type="java.lang.Integer"
        column="MODIFIED"
        length="10"
    />
    <property
        name="modifiedby"
        type="java.lang.Integer"
        column="MODIFIEDBY"
        length="10"
    />
    <property
        name="orderqty"
        type="java.lang.Integer"
        column="ORDERQTY"
        length="10"
    />

    <!-- Associations -->
 
    <!-- bi-directional many-to-one association to Order
    <many-to-one
        name="order"
        class="order_mod.Order"
        not-null="true"
    >
        <column name="ORDERNO" />
    </many-to-one>-->
    <!-- bi-directional many-to-one association to Productscorp
    <many-to-one
        name="productscorp"
        class="order_mod.Productscorp"
        not-null="true"
    >
        <column name="PLUID" />
    </many-to-one>-->

</class>
</hibernate-mapping>

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
    "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd" >
   
<hibernate-mapping>
<!--
    Created by the Middlegen Hibernate plugin 2.1

    http://boss.bekk.no/boss/middlegen/
    http://www.hibernate.org/
-->

<class
    name="order_mod.Order"
    table="ORDERS"
>

    <id
        name="orderno"
        type="java.lang.Integer"
        column="ORDERNO"
    />
   
   
    <property
        name="locno"
        type="java.lang.Integer"
        column="LOCNO"
        length="10"
    />
   
    <property
        name="vendorno"
        type="java.lang.Integer"
        column="VENDORNO"
        length="10"
    />
    <property
        name="vendorname"
        type="java.lang.String"
        column="VENDORNAME"
        length="255"
    />
    <property
        name="status"
        type="java.lang.Integer"
        column="STATUS"
        length="10"
    />
    <property
        name="totalcost"
        type="java.lang.Double"
        column="TOTALCOST"
        length="15"
    />
    <property
        name="shippingcost"
        type="java.lang.Double"
        column="SHIPPINGCOST"
        length="15"
    />
    <property
        name="datecreated"
        type="java.sql.Timestamp"
        column="DATECREATED"
        length="19"
    />
    <property
        name="dateplaced"
        type="java.sql.Timestamp"
        column="DATEPLACED"
        length="19"
    />
    <property
        name="createdby"
        type="java.lang.Integer"
        column="CREATEDBY"
        length="10"
    />
    <property
        name="modifiedby"
        type="java.lang.Integer"
        column="MODIFIEDBY"
        length="10"
    />
    <property
        name="modifiedlast"
        type="java.lang.Integer"
        column="MODIFIEDLAST"
        length="10"
    />
    <property
        name="modified"
        type="java.lang.Integer"
        column="MODIFIED"
        length="10"
    />

    <!-- Associations -->
 
    <!-- bi-directional one-to-many association to Onorder
        lazy="true"
        inverse="true" -->
    <set
        name="onorders"
   cascade="all"
    >
        <key>
            <column name="ORDERNO" />
        </key>
        <one-to-many
            class="order_mod.Onorder"
        />
    </set>

</class>
</hibernate-mapping>

package order_mod;

import java.io.Serializable;
import java.util.Date;
import org.apache.commons.lang.builder.ToStringBuilder;


/** @author order_mod CodeGenerator */
public class Onorder implements Serializable {

    /** identifier field */
    private Integer autono;

    /** nullable persistent field */
    private String plu;
   
     /** identifier field */
    private Integer orderno;
   
    /** nullable persistent field */
    private String itemno;

    /** persistent field */
    private int locno;

    /** persistent field */
    private String description;

    /** nullable persistent field */
    private Integer vendorno;

    /** nullable persistent field */
    private Double projectedcost;

    /** nullable persistent field */
    private Double actualcost;

    /** nullable persistent field */
    private Date dateordered;

    /** nullable persistent field */
    private Date datereceived;

    /** nullable persistent field */
    private Integer modified;

    /** nullable persistent field */
    private Integer modifiedby;

    /** nullable persistent field */
    private Integer orderqty;

    /** persistent field */
    private order_mod.Order order;

    /** full constructor */
    public Onorder(Integer autono, String plu, Integer orderno, String itemno, int locno, String description, Integer vendorno, Double projectedcost, Double actualcost, Date dateordered, Date datereceived, Integer modified, Integer modifiedby, Integer orderqty, order_mod.Order order){
        this.autono = autono;
        this.plu = plu;
        this.orderno = orderno;
        this.itemno = itemno;
        this.locno = locno;
        this.description = description;
        this.vendorno = vendorno;
        this.projectedcost = projectedcost;
        this.actualcost = actualcost;
        this.dateordered = dateordered;
        this.datereceived = datereceived;
        this.modified = modified;
        this.modifiedby = modifiedby;
        this.orderqty = orderqty;
        this.order = order;
        //this.productscorp = productscorp;
    }

    /** default constructor */
    public Onorder() {
    }

    /** minimal constructor */
    public Onorder(Integer autono, int locno, String description, order_mod.Order order)
        this.autono = autono;
        this.locno = locno;
        this.description = description;
        this.order = order;

    }

    public Integer getAutono() {
        return this.autono;
    }

    public void setAutono(Integer autono) {
        this.autono = autono;
    }
   
   public String getPlu() {
        return this.plu;
    }

    public void setPlu(String plu) {
        this.plu = plu;
    }
    public Integer getOrderno() {
        return this.orderno;
    }

    public void setOrderno(Integer orderno) {
        this.orderno = orderno;
    }
    public String getItemno() {
        return this.itemno;
    }

    public void setItemno(String itemno) {
        this.itemno = itemno;
    }

    public int getLocno() {
        return this.locno;
    }

    public void setLocno(int locno) {
        this.locno = locno;
    }

    public String getDescription() {
        return this.description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    public Integer getVendorno() {
        return this.vendorno;
    }

    public void setVendorno(Integer vendorno) {
        this.vendorno = vendorno;
    }

    public Double getProjectedcost() {
        return this.projectedcost;
    }

    public void setProjectedcost(Double projectedcost) {
        this.projectedcost = projectedcost;
    }

    public Double getActualcost() {
        return this.actualcost;
    }

    public void setActualcost(Double actualcost) {
        this.actualcost = actualcost;
    }

    public Date getDateordered() {
        return this.dateordered;
    }

    public void setDateordered(Date dateordered) {
        this.dateordered = dateordered;
    }

    public Date getDatereceived() {
        return this.datereceived;
    }

    public void setDatereceived(Date datereceived) {
        this.datereceived = datereceived;
    }

    public Integer getModified() {
        return this.modified;
    }

    public void setModified(Integer modified) {
        this.modified = modified;
    }

    public Integer getModifiedby() {
        return this.modifiedby;
    }

    public void setModifiedby(Integer modifiedby) {
        this.modifiedby = modifiedby;
    }

    public Integer getOrderqty() {
        return this.orderqty;
    }

    public void setOrderqty(Integer orderqty) {
        this.orderqty = orderqty;
    }

    public order_mod.Order getOrder() {
        return this.order;
    }

    public void setOrder(order_mod.Order order) {
        this.order = order;
    }

    public String toString() {
        return new ToStringBuilder(this)
            .append("autono", getAutono())
            .toString();
    }

}

package order_mod;

import java.io.Serializable;
import java.util.Date;
import java.util.Set;
import org.apache.commons.lang.builder.ToStringBuilder;
import java.util.List;
import java.util.HashSet;

/** @author Hibernate CodeGenerator */
public class Order implements Serializable {
   
    /** identifier field */
    private Integer orderno;
   
    /** nullable persistent field */
    private Integer locno;
   
    /** nullable persistent field */
    private Integer vendorno;
   
    /** nullable persistent field */
    private String vendorname;
   
    /** nullable persistent field */
    private Integer status;
   
    /** nullable persistent field */
    private Double totalcost;
   
    /** nullable persistent field */
    private Double shippingcost;
   
    /** nullable persistent field */
    private Date datecreated;
   
    /** nullable persistent field */
    private Date dateplaced;
   
    /** nullable persistent field */
    private Integer createdby;
   
    /** nullable persistent field */
    private Integer modifiedby;
   
    /** nullable persistent field */
    private Integer modifiedlast;
   
    /** nullable persistent field */
    private Integer modified;
   
    /** persistent field */
    private Set onorders;
   
    /** full constructor */
    public Order(Integer orderno, Integer locno, Integer vendorno, String vendorname, Integer status, Double totalcost, Double shippingcost, Date datecreated, Date dateplaced, Integer createdby, Integer modifiedby, Integer modifiedlast, Integer modified, Set onorders) {
        this.orderno = orderno;
        this.locno = locno;
        this.vendorno = vendorno;
        this.vendorname = vendorname;
        this.status = status;
        this.totalcost = totalcost;
        this.shippingcost = shippingcost;
        this.datecreated = datecreated;
        this.dateplaced = dateplaced;
        this.createdby = createdby;
        this.modifiedby = modifiedby;
        this.modifiedlast = modifiedlast;
        this.modified = modified;
        this.onorders = onorders;
    }
   
    /** default constructor */
    public Order() {
       
    }
   
    /** minimal constructor */
    public Order(Integer orderno, Set onorders) {
        this.orderno = orderno;
        this.onorders = onorders;
    }
   
    public Integer getOrderno() {
        return this.orderno;
    }
   
    public void setOrderno(Integer orderno) {
        this.orderno = orderno;
    }
    public Integer getLocno() {
        return this.locno;
    }
   
    public void setLocno(Integer locno) {
        this.orderno = locno;
    }
    public Integer getVendorno() {
        return this.vendorno;
    }
   
    public void setVendorno(Integer vendorno) {
        this.vendorno = vendorno;
    }
   
    public String getVendorname() {
        return this.vendorname;
    }
   
    public void setVendorname(String vendorname) {
        this.vendorname = vendorname;
    }
   
    public Integer getStatus() {
        return this.status;
    }
   
    public void setStatus(Integer status) {
        this.status = status;
    }
   
    public Double getTotalcost() {
        return this.totalcost;
    }
   
    public void setTotalcost(Double totalcost) {
        this.totalcost = totalcost;
    }
   
    public Double getShippingcost() {
        return this.shippingcost;
    }
   
    public void setShippingcost(Double shippingcost) {
        this.shippingcost = shippingcost;
    }
   
    public Date getDatecreated() {
        return this.datecreated;
    }
   
    public void setDatecreated(Date datecreated) {
        this.datecreated = datecreated;
    }
   
    public Date getDateplaced() {
        return this.dateplaced;
    }
   
    public void setDateplaced(Date dateplaced) {
        this.dateplaced = dateplaced;
    }
   
    public Integer getCreatedby() {
        return this.createdby;
    }
   
    public void setCreatedby(Integer createdby) {
        this.createdby = createdby;
    }
   
    public Integer getModifiedby() {
        return this.modifiedby;
    }
   
    public void setModifiedby(Integer modifiedby) {
        this.modifiedby = modifiedby;
    }
   
    public Integer getModifiedlast() {
        return this.modifiedlast;
    }
   
    public void setModifiedlast(Integer modifiedlast) {
        this.modifiedlast = modifiedlast;
    }
   
    public Integer getModified() {
        return this.modified;
    }
   
    public void setModified(Integer modified) {
        this.modified = modified;
    }
   
    public Set getOnorders() {
        return this.onorders;
    }
   
    public void setOnorders(Set onorders) {
        this.onorders = onorders;
    }
   
    public void addOnorder(Onorder onorder){
        try{
            if((onorders == null)){
                onorders = new HashSet();
            }else if((onorders.size()<0) || (onorders.isEmpty())){
                onorders = new HashSet();
            }
            onorders.add(onorder);
        }catch(Exception e){
            System.err.println("order_mod.Order.addOnorder():" + e.toString());
            e.printStackTrace();
        }
    }
   
    public String toString() {
        return new ToStringBuilder(this)
        .append("orderno", getOrderno())
        .toString();
    }
   
}