JSF page doesnot work when i add selectOneMenu (prime faces) - jsf

Question

i have a managed bean called Lecturer. Lecturer managed bean includes a relation between departments. I want to show all departments stored in the database. when i register a lecturer i need to get its department.
My Lecturer managed bean. i have proper setter and getter methods. i just omit it for clarification.
public class Lecturer
{
private String name;
private String surname;
private String email;
private String username;
private String password;
private List<Department> departments;
private LecturerService lecturerService;
private DepartmentService departmentService;
}
my Licturer.xhtml file:
<h:form>
<f:view>
<p:panelGrid columns="2">
<f:facet name="header">Lecturer Registration Form</f:facet>
<h:outputLabel for="name" value="Name :" />
<p:inputText id="name" value="#{Lecturer.name}" label="Name" required="true" />
<h:outputLabel for="surname" value="Surname :" />
<p:inputText id="surname" value="#{Lecturer.surname}" label="Surname" required="true" />
<h:outputLabel for="department" value="Department :" />
<p:selectOneMenu value="#{Lecturer.departments}" effect="fade" editable="true" var="p" >
<f:selectItem itemLabel="Select One" itemValue="" />
<f:selectItems value="#{Lecturer.departments}" var="lec"
itemLabel="#{lec.name}" itemValue="#{lec.name}"/>
</p:selectOneMenu>
<h:outputLabel for="email" value="Email :" />
<p:inputText id="email" value="#{Lecturer.email}" label="Email" required="true" />
<h:outputLabel for="username" value="User Name :" />
<p:inputText id="username" value="#{Lecturer.username}" label="Email" required="true" />
<h:outputLabel for="password" value="Password :" />
<p:inputText id="password" value="#{Lecturer.password}" label="Password" required="true" />
<f:facet name="footer">
<p:commandButton type="submit"
id="lecturer"
action="#{Lecturer.registerLecturer}"
value="Register" icon="ui-icon-disk">
</p:commandButton>
</f:facet>
</p:panelGrid>
</f:view>
</h:form>
my faces-config.xml
<managed-bean>
<managed-bean-name>Lecturer</managed-bean-name>
<managed-bean-class>com.studinfo.controller.Lecturer</managed-bean-class>
<managed-bean-scope>session</managed-bean-scope>
<managed-property>
<property-name>departmentService</property-name>
<property-class>com.studinfo.services.DepartmentService</property-class>
<value>#{DepartmentService}</value>
</managed-property>
<managed-property>
<property-name>lecturerService</property-name>
<property-class>com.studinfo.services.LecturerService</property-class>
<value>#{LecturerService}</value>
</managed-property>
</managed-bean>
when i remove the selectOneMenu tag. my page works properly.
any idea about the solution?
Do i must add a converter between string and Department class?

Answer 1

The value attribute of p:selectOneMenu should hold the reference to a single department (this is the selected department) and not the whole list. You need to add a field for this in your bean, e.g.:
private Department selectedDepartment
// getter and setter
Then in your facelet change the value attribute of p:selectOneMenu and the f:selectItems:
<p:selectOneMenu value="#{Lecturer.selectedDepartment}" effect="fade"
editable="true" var="p" >
<f:selectItem itemLabel="Select One" itemValue="" />
<f:selectItems value="#{Lecturer.departments}" var="lec"
itemLabel="#{lec.name}" itemValue="#{lec}"/>
</p:selectOneMenu>
Furthermore you will need a converter to map selected strings to objects.