Problems with WebDataBinder and Set.Class

[stunaz]

Hello everyone, i am having trouble with binding my data from a form :
I have two class

@Entity
@Table(name = "ROLES")
public class Role implements GenericDomain {

private Long id;
private String code;
private String name;

private Set<Privilege> privileges = new HashSet<Privilege>(0);

public Role() {}

/* getter and setter*/

@ManyToMany(cascade=CascadeType.ALL)
@JoinTable(name = "ROLES_PRIVILEGES"
, joinColumns = { @JoinColumn(name = "ROLE_ID") }
, inverseJoinColumns = { @JoinColumn(name = "PRIVILEGE_ID") }
)

public Set<Privilege> getPrivileges() {
return this.privileges;
}
public void setPrivileges(Set<Privilege> privileges) {
this.privileges = privileges;
}
/* overide of hascode, equals*/
}
And

@Entity
@Table(name = "PRIVILEGES")
public class Privilege implements GenericDomain {

private Long id;
private String code;

private Set<Role> roles = new HashSet<Role>(0);

public Privilege() {}

/* getter and setter*/

@ManyToMany(cascade=CascadeType.REFRESH, mappedBy="privileges")
public Set<Role> getRoles() {
return this.roles;
}
public void setRoles(Set<Role> roles) {
this.roles = roles;
}
@Override
public String toString(){
return this.getCode() + this.getComment();
}

/*overide equals and hascode*/
and in my controller i have :

@InitBinder
public void initBinder(WebDataBinder binder) {

binder.registerCustomEditor(Set.class, "privileges", new
CustomCollectionEditor(Set.class) {
@Override
protected Object convertElement(Object element) {
return (element == null)?
nullrivilegeService.getOne(Integer.parseInt((String)element));
}
});
}
@RequestMapping(value = "edit", method = RequestMethod.POST)
public String saveOldRole( @ModelAttribute("role") Role role
, BindingResult result
, ModelMap model
) {

validator.validate(role, result);
if (result.hasErrors()){
logger.error(result.getAllErrors());
model.addAllAttributes(result.getModel());
return "/admin/role/edit";
}
logger.info(role.getPrivileges());
Iterator p = role.getPrivileges().iterator();
while(p.hasNext()){
logger.info(p.next().getClass());
}
roleService.saveOrUpdate(role);
model.addAttribute("roles", roleService.getAll());
sessionStatus.setComplete();
return "redirect:/admin/role/list.do";
}
and my debug is

role.RoleController:93 - [[MANAGE_USERS], [MANAGE_ROLES]]
role.RoleController:96 - class java.util.LinkedHashSet
role.RoleController:96 - class java.util.LinkedHashSet
22:29:44,915 ERROR tomcat-http--7 property.BasicPropertyAccessor:194 -
IllegalArgumentException in class: com.stunaz.domain.Privilege, getter
method of property: id
I dont understand why at 96, the class type is
java.util.LinkedHashSet, i thought it should be Privileges. I dont
understand why my role.getPrivileges() is a Set of Set, it should be a
Set of Privilege.

Of course at saveOrUpdate am getting an error.