Problems with WebDataBinder and Set.Class

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)?
null:privilegeService.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.