Свойство Not-null ссылается на временное значение при вставке нового деманда

Question

Я пытаюсь сохранить новый demande в базе данных, у меня есть выпадающий список в jsp, который дает мне существующий тип demande из DB. У demande есть идентификатор (первичный ключ), пользователь demande (пользователь внешнего ключа), тип demande (тип внешнего ключа demande). на странице jsp существующие списки работают нормально, хотя ..
это ошибка в спящем режиме дает мне:

WARN  UnresolvedEntityInsertActions - HHH000437: Attempting to save one or more entities that have a non-nullable association with an unsaved transient entity. The unsaved transient entity must be saved in an operation prior to saving these dependent entities.
    Unsaved transient entity: ([jpa.project.model.DemTypeDemande#0])
    Dependent entities: ([[jpa.project.model.DemDemande#150]])
    Non-nullable association(s): ([jpa.project.model.DemDemande.demTypeDemande])

tomcat:

HTTP Status 500 - Request processing failed; nested exception is org.hibernate.TransientPropertyValueException: Not-null property references a transient value - transient instance must be saved before current operation: jpa.project.model.DemDemande.demTypeDemande -> jpa.project.model.DemTypeDemande

РЕДАКТИРОВАТЬ: Контроллер:

@Controller
public class DemandeController {
	@Autowired
ProjectService service ;
	
	@RequestMapping(value = "/demandes/manage",method = RequestMethod.GET)
	public ModelAndView manageUsers(HttpServletRequest request) throws IOException {
		//set view
		ModelAndView model = new ModelAndView();		
		model.setViewName("managedemandes");
		//set users list
	    List<DemDemande> listDemandes = service.getDemandes();
		model.addObject("listDemandes", listDemandes);		
		
		//set types demande list
	   List<DemTypeDemande> listTypeDemandes = service.getTypeDemandes();
	   model.addObject("listTypeDemandes", listTypeDemandes); 				  
	 //retrieve  user
	   String ConnectedUsername = service.getConnectedUsername(request);	   
	   DemUser currentUser = service.getUserByUsername(ConnectedUsername);
	   model.addObject("demUser", currentUser); 
	  
	   //add demande object 
	   model.addObject("DemDemande", new DemDemande()); 

		return model;
	}
	
	
	@RequestMapping(value = "/demandes/actionadddemande", method = RequestMethod.POST)
	public String actionadduser(@ModelAttribute("DemTypeDemande") DemTypeDemande TypeDemande,
			@ModelAttribute("demUser") DemUser DemUser
			,@ModelAttribute("DemDemande") DemDemande demande,BindingResult result) {
		   
		
	    demande.setDemUser(DemUser);  
	    demande.setDemTypeDemande(TypeDemande);
        service.addDemande(demande);
		return "redirect:/demandes/manage";
	}
	
}

объект demande:

@Entity
@Table(name="DEM_DEMANDE")
@NamedQuery(name="DemDemande.findAll", query="SELECT d FROM DemDemande d")
public class DemDemande implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    @SequenceGenerator(name="DEM_DEMANDE_IDDEMANDE_GENERATOR", sequenceName="SEQ_DEM_DEMANDE")
    @GeneratedValue(strategy=GenerationType.SEQUENCE, generator="DEM_DEMANDE_IDDEMANDE_GENERATOR")
    @Column(name="ID_DEMANDE", unique=true, nullable=false)
    private long idDemande;

    //uni-directional many-to-one association to DemTypeDemande
    @ManyToOne
    @JoinColumn(name="ID_TYPE_DEMANDE", nullable=false)
    private DemTypeDemande demTypeDemande;

    //uni-directional many-to-one association to DemUser
    @ManyToOne
    @JoinColumn(name="ID_DEM_USER", nullable=false)
    private DemUser demUser;

    public DemDemande() {
    }

    public long getIdDemande() {
        return this.idDemande;
    }

    public void setIdDemande(long idDemande) {
        this.idDemande = idDemande;
    }

    public DemTypeDemande getDemTypeDemande() {
        return this.demTypeDemande;
    }

    public void setDemTypeDemande(DemTypeDemande demTypeDemande) {
        this.demTypeDemande = demTypeDemande;
    }

    public DemUser getDemUser() {
        return this.demUser;
    }

    public void setDemUser(DemUser demUser) {
        this.demUser = demUser;
    }

}

тип объекта demande:

@Entity
@Table(name="DEM_TYPE_DEMANDE")
@NamedQuery(name="DemTypeDemande.findAll", query="SELECT d FROM DemTypeDemande d")
public class DemTypeDemande implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    @SequenceGenerator(name="DEM_TYPE_DEMANDE_IDTYPEDEMANDE_GENERATOR", sequenceName="SEQ_DEM_TYPE_DEMANDE")
    @GeneratedValue(strategy=GenerationType.SEQUENCE, generator="DEM_TYPE_DEMANDE_IDTYPEDEMANDE_GENERATOR")
    @Column(name="ID_TYPE_DEMANDE", unique=true, nullable=false)
    private long idTypeDemande;

    @Column(name="LIB_TYPE_DEMANDE", nullable=false, length=100)
    private String libTypeDemande;

    public DemTypeDemande() {
    }

    public long getIdTypeDemande() {
        return this.idTypeDemande;
    }

    public void setIdTypeDemande(long idTypeDemande) {
        this.idTypeDemande = idTypeDemande;
    }

    public String getLibTypeDemande() {
        return this.libTypeDemande;
    }

    public void setLibTypeDemande(String libTypeDemande) {
        this.libTypeDemande = libTypeDemande;
    }

}

объект пользователя:

@Entity
@Table(name="DEM_USER")
@NamedQuery(name="DemUser.findAll", query="SELECT d FROM DemUser d")
public class DemUser implements Serializable {
    private static final long serialVersionUID = 1L;

    @Id
    @SequenceGenerator(name="DEM_USER_IDUSER_GENERATOR", sequenceName="SEQ_DEM_USER")
    @GeneratedValue(strategy=GenerationType.SEQUENCE, generator="DEM_USER_IDUSER_GENERATOR")
    @Column(name="ID_USER", unique=true, nullable=false)
    private long idUser;

    @Column(name="NAME_USER", nullable=false, length=50)
    private String nameUser;

    @Column(nullable=false, length=20)
    private String password;

    //uni-directional many-to-one association to DemRole
    @ManyToOne
    @JoinColumn(name="ID_ROLE", nullable=false)
    private DemRole demRole;

    public DemUser() {
    }

    public long getIdUser() {
        return this.idUser;
    }

    public void setIdUser(long idUser) {
        this.idUser = idUser;
    }

    public String getNameUser() {
        return this.nameUser;
    }

    public void setNameUser(String nameUser) {
        this.nameUser = nameUser;
    }

    public String getPassword() {
        return this.password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public DemRole getDemRole() {
        return this.demRole;
    }

    public void setDemRole(DemRole demRole) {
        this.demRole = demRole;
    }

}

JSP:

<%@page contentType="text/html" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
   "http://www.w3.org/TR/html4/loose.dtd">
   <%@ taglib prefix="form" uri="http://www.springframework.org/tags/form"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<%@ taglib prefix="sec" uri="http://www.springframework.org/security/tags" %>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Insert title here</title>
</head>
<body>
	    <div align="left">
This is manage Demandes
<table border="1">
        <h1>Demandes</h1>
			<tr><td> id demande </td> <td> Type demande :</td>  <td>  Nom demandeur :</td></tr>
			<c:forEach var="demande" items="${listDemandes}">
				<tr>
					<td>${demande.idDemande}</td>			
					<td>${demande.demTypeDemande.libTypeDemande}</td>								
					<td>${demande.demUser.nameUser}</td>			
				</tr>	
			</c:forEach>
		</table>
			    </div>
			    
			    
	    <div align="center">	    
        <h1>New user</h1>
        <form:form action="actionadddemande" method="POST" modelAttribute="DemDemande">
        <table>
                    <form:hidden path="idDemande" />
                     <form:hidden path="demUser"  />          
     			<tr>
				<td>Types :</td>
				<td>
  <form:select path="demTypeDemande">
         <form:options items="${listTypeDemandes}"  itemValue="idTypeDemande" itemLabel="libTypeDemande"></form:options>
    </form:select></td>
</tr>
            <tr>
                <td colspan="2" align="center"><input type="submit" value="Save"></td>
            </tr>
        </table>
        </form:form>
        </div>

</body>
</html>