Question

I’m working on a test application using Spring MVC.
I have a Person class and a Group class. Every Person object references a Group object.

Now I implemented a jsp that show Person data and allow editing. Inside my form i put a select control to select the pearson’s group:

<sf:select path="group">
    <sf:options items="${groupList}" itemLabel="name" itemValue="id" />
</sf:select>

It shows the correct group when I load the page, but I cannot save changes, because in the controller I get only the string representing the group id.

So, my question is: how can I obtain a Group object instead of its id in my controller?

UPDATE
Here my controller code:

@RequestMapping(value = "/details", params = "save", method = RequestMethod.POST)
public String save(@ModelAttribute("person") Person p,
        BindingResult result) {
    this.personManager.savePerson(p);
    return "redirect:/people/details?id=" + p.getId();
}

Answer 1

Create your own GroupEditor (that will populate the group object instance correcty) by extending PropertyEditorSupport. Then bind that in your controller :

@InitBinder
protected void initBinder(WebDataBinder binder)     {
      binder.registerCustomEditor(Group.class, new GroupEditor(groupService));
}

and your actual editor could look somethign like this :

public class GroupEditor extends PropertyEditorSupport{

    private final GroupService groupService;

    public GroupEditor(GroupService groupService){
        this.groupService= groupService;
    }

    @Override
    public void setAsText(String text) throws IllegalArgumentException {
      Group group = groupService.getById(Integer.parseInt(text));
      setValue(group);
    }
}

Spring docs