how to add arraylist contents to menu in jsf 2 - jsf-2

Question

I want to add the contents of an arraylist has meu in a jsf page but playing me anything can you help me !!!! thnks
this is the method where i fill my arraylist from database in bean
public List<String> profession_pere_list;
public String profession_pere;
//....setters & getters
public List<String> getSelectProfessions() throws SQLException, NamingException{
profession_pere_list = new ArrayList<String>();
initctx = (Context) new InitialContext();
Context envContext = (Context) initctx.lookup("java:comp/env");
ds = (DataSource) envContext.lookup("jdbc/reinscription");
cnx = ds.getConnection();
state = cnx.createStatement();
rst = state.executeQuery("select profession from professions");
while(rst.next())
{
etu = new etudiants();
prof =rst.getString(1);
etu.setProfession_pere(prof);
//profession_pere=prof;
//etu.setProfession_pere(rst.getString(1).toString());
profession_pere_list.add(prof);
}
return profession_pere_list;}
and my jsf page:
<h:selectOneMenu value="#{etudiants.profession_pere}">
<f:selectItems value="#{etudiants.profession_pere_list}"/>
so i have this error unknown source !!!
javax.servlet.ServletException
javax.faces.webapp.FacesServlet.service(Unknown Source)
cause mère
java.lang.NullPointerException
com.sun.faces.renderkit.SelectItemsIterator$GenericObjectSelectItemIterator$GenericObjectSelectItem.updateItem(Unknown Source)
com.sun.faces.renderkit.SelectItemsIterator$GenericObjectSelectItemIterator$GenericObjectSelectItem.access$600(Unknown Source)
com.sun.faces.renderkit.SelectItemsIterator$GenericObjectSelectItemIterator.getSelectItemFor(Unknown Source)
com.sun.faces.renderkit.SelectItemsIterator$IterableItemIterator.next(Unknown Source)
com.sun.faces.renderkit.SelectItemsIterator$IterableItemIterator.next(Unknown Source)
com.sun.faces.renderkit.SelectItemsIterator.next(Unknown Source)
com.sun.faces.renderkit.html_basic.MenuRenderer.renderOptions(Unknown Source)
com.sun.faces.renderkit.html_basic.MenuRenderer.renderSelect(Unknown Source)
com.sun.faces.renderkit.html_basic.MenuRenderer.encodeEnd(Unknown Source)
javax.faces.component.UIComponentBase.encodeEnd(Unknown Source)
javax.faces.component.UIComponent.encodeAll(Unknown Source)
javax.faces.component.UIComponent.encodeAll(Unknown Source)
com.sun.faces.application.view.FaceletViewHandlingStrategy.renderView(Unknown Source)
com.sun.faces.application.view.MultiViewHandler.renderView(Unknown Source)
com.sun.faces.lifecycle.RenderResponsePhase.execute(Unknown Source)
com.sun.faces.lifecycle.Phase.doPhase(Unknown Source)
com.sun.faces.lifecycle.LifecycleImpl.render(Unknown Source)
javax.faces.webapp.FacesServlet.service(Unknown Source)

Answer 1

I had the same issue and the rason was a List modified concurently by different HTTP threads in ViewScoped bean:
#ViewScoped
public class Bean {
private List<Object> list;
public List<Object> getList() {
this.list = new ArrayList<>();
// code which modifies list
return this.list;
}
}
Solution - synchronize access to list:
public synchronized List<Object> getList() {
In my case I had sometimes your exception and sometimes ConcurrentModificationException.
I have also found another explanation:
http://www.adam-bien.com/roller/abien/entry/jsf_nullpointerexception_in_selectitemsiterator_java
When SelectItem label is null - you can also get your exception.