Hibernate+JSF +Mysql

Witam
Proboje zapisac cos do bazy danych za pomoca hibernate i pojawia sie blad:
org.hibernate.exception.GenericJDBCException: could not insert: [model.Employee]

gdy robię odczyt z bazy i usuniecie z bazy wszystko działa poprawnie

 
/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */

package beans;

import hib.HibernateUtil;
import java.util.List;
import javax.faces.bean.ManagedBean;
import javax.faces.bean.RequestScoped;
import model.Employee;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.Transaction;
   import javax.faces.context.FacesContext;

/**
 *
 * @author marezo
 */
@ManagedBean
@RequestScoped
public class JSFManagedBean {
   private String n;
   private int id;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getN() {
        return n;
    }

    public void setN(String n) {
        this.n = n;
    }
   

    /** Creates a new instance of JSFManagedBean */
    public JSFManagedBean() {
    }
      public void addProdukt(int id, String n) {
        SessionFactory sf = HibernateUtil.getSessionFactory();
        Session s = sf.openSession();
        Transaction tx = s.beginTransaction();
        
        Employee p = new Employee();
        p.setId(id);
        p.setName(n);
        

        s.save(p);

        tx.commit();
        s.close();
         
    }
      public String dodaj()
    {
        addProdukt(id, n);
        n = null;
        id = 0;
        return null;

}
      public List<Employee> getProdukty() {
        SessionFactory sf = HibernateUtil.getSessionFactory();
        Session s = sf.openSession();
        List<Employee> pp =(List<Employee>)s.createQuery("SELECT e FROM Employee e").list();
        s.close();
        return pp;
    }
      public void deleteProdukt(Integer pid) {
        SessionFactory sf = HibernateUtil.getSessionFactory();
        Session s = sf.openSession();
        Transaction tx = s.beginTransaction();
        Employee p = (Employee) s.get(Employee.class, pid);
        s.delete(p);
        tx.commit();
        s.close();
    }
      public String usun() {
        FacesContext context = FacesContext.getCurrentInstance();
        String spid = context.getExternalContext().getRequestParameterMap().get("pid");
        Integer pid = Integer.parseInt(spid);
        deleteProdukt(pid);
        return null;
    }

}

.

Klasa /*

package model;

import java.io.Serializable;
import javax.persistence.Basic;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.NamedQueries;
import javax.persistence.NamedQuery;
import javax.persistence.Table;

/**
*

@Author marezo
*/
@Entity
@Table(name = "employee")
@NamedQueries({
@NamedQuery(name = "Employee.findAll", query = "SELECT e FROM Employee e")})
public class Employee implements Serializable {
private static final long serialVersionUID = 1L;
@Id
@basic(optional = false)
@Column(name = "id")
private Integer id;
@Column(name = "name")
private String name;

public Employee() {
}

public Employee(Integer id) {
this.id = id;
}

public Integer getId() {
return id;
}

public void setId(Integer id) {
this.id = id;
}

public String getName() {
return name;
}

public void setName(String name) {
this.name = name;
}
}
</CODE>
mapowANIE:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
  <class name="model.Employee" table="employee">
           <id name="id" type="int" column="id">
    <generator class="native" />
  </id>
 <property name="name" column="name" type="string" not-null="true" />

</class>


</hibernate-mapping>

Czy ktoś wie może co zrobiłem nie tak?