hibernate - 実行時エラー:org.hibernate.exception.ConstraintViolationException: JDBC バッチ更新を実行できませんでした

Question

繰り返しますが、私はこの問題を抱えており、ここで立ち往生しています。すぐ下のコードはサーブレットです。

AnnotationConfiguration ac=new AnnotationConfiguration();
                    ac.addAnnotatedClass(Client.class);
                    ac.addAnnotatedClass(Inventory.class);
                    ac.addAnnotatedClass(Ledger.class);
                    ac.addAnnotatedClass(QuantityBought.class);
                    ac.configure();
                    SessionFactory factory=ac.buildSessionFactory();
                    Session session=factory.openSession();
                    Client client=(Client)session.get(Client.class, Integer.parseInt(request.getParameter("cid")));

                    client.setBalance(Float.parseFloat(request.getParameter("balance")));

                    Ledger ledger=new Ledger();

                    Date d=new Date();

                    ledger.setDate_of_purchase(d);
                    int total=0;
                    for(int l=1;l<6;l++)
                    {   
                     if(request.getParameter("id"+l)!=null)
                     {

                         Inventory inventory=(Inventory)session.get(Inventory.class, Integer.parseInt(request.getParameter("id"+l)));

                         total=total+(int)(Integer.parseInt(request.getParameter("crate"+l))*inventory.getTrade()+Integer.parseInt(request.getParameter("botle"+l))*(inventory.getMrp()/inventory.getSize_of_crate()));

                         QuantityBought bought=new QuantityBought();

                         bought.setProduct(inventory.getName());

                         bought.setQuantity_bought(Integer.parseInt(request.getParameter("crate"+l))*inventory.getSize_of_crate()+Integer.parseInt(request.getParameter("botle"+l)));

                         bought.setSize_of_quantity(inventory.getSize_bottle());

                         bought.setTotal(Integer.parseInt(request.getParameter("crate"+l))*inventory.getTrade()+Integer.parseInt(request.getParameter("botle"+l))*(inventory.getMrp()/inventory.getSize_of_crate()));

                         bought.setBelongs_to_ledger(ledger);

                         inventory.setQuantity_available(inventory.getQuantity_available()-(Integer.parseInt(request.getParameter("crate"+l))*inventory.getSize_of_crate()+Integer.parseInt(request.getParameter("botle"+l))));

                         session.beginTransaction().begin();

                         session.save(bought);


                         session.saveOrUpdate(inventory);

                         session.beginTransaction().commit();
                     }
                    }

                    ledger.setSum_total(total);

                    client.getLedger().add(ledger);

                    session.beginTransaction().begin();

                    session.saveOrUpdate(client);
                    session.save(ledger);

                    session.beginTransaction().commit();

    } 

クライアント。クラス

@Entity
public class Client implements Serializable {
private String Name;
private String Address;
private float balance;
@Id
@GeneratedValue
private int client_id;

@OneToMany(targetEntity=Ledger.class,mappedBy="client",cascade= CascadeType.ALL)
private List<Ledger> ledger;
}

元帳.クラス

@Entity
public class Ledger implements Serializable {
@Id
private int id;
@ManyToOne
private Client client;
private Date date_of_purchase;

@OneToMany(targetEntity=QuantityBought.class,mappedBy="belongs_to_ledger",cascade= CascadeType.ALL)
private List<QuantityBought> quantitybought;
private float sum_total;
}

QuantityBought.class

@Entity
public class QuantityBought implements Serializable {
@Id
@GeneratedValue
private int id;

private String product;
private int size_of_quantity;
private int quantity_bought;

@ManyToOne
private Ledger belongs_to_ledger;  

private float total;}

実行時にこのエラーが発生します。QuantityBought のオブジェクトの保存中。何が悪いのか理解できません。

org.hibernate.exception.ConstraintViolationException: Could not execute JDBC batch update