org.springframework.web.util.NestedServletException Netbeans - spring

Question

I am using Spring Framework to develop a web app.
The problem is when i tried to add an article in my database It shows a NestedServlet exception. Can any one help me ?
This is my controler class :
#Controller
public class Controler {
ArticleFacadeLocal articleModel;
CategorieFacadeLocal categorieModel;
ConnexionFacadeLocal connexionModel;
public Controler(){
articleModel = new ArticleModel();
categorieModel = new CategorieModel();
connexionModel = new ConnexionModel();
}
#RequestMapping("/home.do")
public String home(HttpServletRequest request){
if(isConnected(request))
return addPage(request);
else return "page:login";
}
#RequestMapping("login.do")
public String login(HttpServletRequest request){
String login=request.getParameter("login");
String password=request.getParameter("password");
if(ConnexionModel.connect(login, password)){
request.getSession().setAttribute("login",login);
ServletContext application=request.getServletContext();
application.setAttribute("categories", categorieModel.findAll());
return addPage(request);}
else
request.setAttribute("error",true);
return "forward:/home.do";
}
#RequestMapping("logout.do")
public String logout(HttpServletRequest request) {
request.getSession(false).invalidate();
return "forward:/home.do";
}
#RequestMapping("articles.do")
public String list(HttpServletRequest request){
request.setAttribute("articles",articleModel.findAll());
return "page:articles";
}
#RequestMapping("addPage.do")
public String addPage(HttpServletRequest request){
request.setAttribute("categories", categorieModel.findAll());
return "page:add";
}
#RequestMapping("add.do")
public String add(HttpServletRequest request){
try{
Article a=getArticleFromView(request);
articleModel.create(a);
request.setAttribute("error", false);
}catch(Exception e){request.setAttribute("error", true);}
return "forward:/addPage.do";
}
#RequestMapping("modifyPage.do")
public String modiyPage(HttpServletRequest request){
int idArticle=Integer.parseInt(request.getParameter("idArticle"));
request.setAttribute("categories", categorieModel.findAll());
Article article = articleModel.find(idArticle);
request.setAttribute("article", article);
return "page:modify";
}
#RequestMapping("modify.do")
public String modify(HttpServletRequest request){
try{
Article a=getArticleFromView(request);
articleModel.edit(a);
return "forward:/articles.do";
}catch(Exception e){
request.setAttribute("error", true);
return "forward:/modifyPage.do";
}
}
#RequestMapping("searchPage.do")
public String searchPage(HttpServletRequest request){
return "page:search";
}
#RequestMapping("search.do")
public String search(HttpServletRequest request){
String libelle=request.getParameter("libelle");
request.setAttribute("article",articleModel.find(libelle));
return "page:search";
}
public boolean isConnected(HttpServletRequest request){
HttpSession session = request.getSession(false);//recupere une session sans la creer
return (session!=null && session.getAttribute("login")!=null);
}
public Article getArticleFromView(HttpServletRequest request){
Article a = new Article();
String libelle = request.getParameter("libelle");
String description = request.getParameter("description");
String prix = request.getParameter("prix");
String qte = request.getParameter("qte");
String categorie = request.getParameter("categorie");
a.setLibelle(libelle);
a.setDescription(description);
a.setPrix(Double.parseDouble(prix));
a.setQte(Integer.parseInt(qte));
a.setCategorie(new Categorie(categorie));
return a;
}
}
And this is my jsp file
<%#include file="include.jsp" %>
<form action="add.do" method="post">
<table align="center">
<tr >
<td>Libelle :
<td><input type="text" required="required" name="libelle"/>
</tr>
<tr >
<td>Description :
<td><input type="text" required="required" name="description">
</tr>
<tr>
<td>Prix :
<td><input type="text" required="required" name="prix">
</tr>
<tr>
<td>Quantité :
<td><input type="text" required="required" name="qte">
</tr>
<tr >
<td> Catégorie :
<td>
<select name="categorie" >
<c:forEach items="${categories}" var="c">
<option value="${c.idCategorie}"> ${c.libelleCategorie} </option>
</c:forEach>
</select>
</tr>
<tr align="center" >
<td colspan="2"><button type="submit" id="btn">Ajouter</button></td>
</tr>
</table>
</form>
<c:if test="${not empty error && error}"> <p style="color: red;"> Echec d'ajout de l'article </p></c:if>
<c:if test="${not empty error && not error}"> <p style="color: green;">Article ajouté avec succes </p></c:if>
This is error exception :
org.springframework.web.util.NestedServletException: Request processing failed; nested exception is org.hibernate.AssertionFailure: null id in model.beans.Article entry (don't flush the Session after an exception occurs)
cause première
org.hibernate.AssertionFailure: null id in model.beans.Article entry (don't flush the Session after an exception occurs)
I am not using Maven.