Automagically bind enum values to OptionGroup items

Vaadin 6 / 7 / 8 Framework UI
1

Hi,

I’ve a very simple enum and a bean class that has it as a member field:

public enum State{ OFFLINE(0), ONLINE(1); private int id; private State(int anId){ id = anId; } } //... public MyBean{ State state; //getters,setters and other code } Now I’m creating the corresponding Form by binding it to the bean using a BeanFieldGroup. The following code works:

MyBean bean = //some initialization here

final BeanFieldGroup<MyBean> binder = new BeanFieldGroup<MyBean>(MyBean.class);
binder.setItemDataSource(bean);
       
OptionGroup stateGroup = new OptionGroup();
stateGroup.setCaption("State");
stateGroup.addItem(State.OFFLINE);
stateGroup.addItem(State.ONLINE);
binder.bind(stateGroup, "state");
mainLayout.addComponent(stateGroup);

//other bindings

However, I found it too complicated. I’d like to follow the “buildAndBind” way, which seems simpler. Something like that:

mainLayout.addComponent(binder.buildAndBind("State","state"));

But it doesn’t work. Vaadin doesn’t know how to handle the enum in a Field. This is the error:

Caused by: com.vaadin.data.fieldgroup.FieldGroup$BindException: Unable to build a field of type com.vaadin.ui.Field for editing com.acme.State
    at com.vaadin.data.fieldgroup.FieldGroup.build(FieldGroup.java:1067)
    at com.vaadin.data.fieldgroup.FieldGroup.buildAndBind(FieldGroup.java:1039)
    at com.vaadin.data.fieldgroup.FieldGroup.buildAndBind(FieldGroup.java:1017)
    at com.vaadin.data.fieldgroup.BeanFieldGroup.buildAndBind(BeanFieldGroup.java:170)

I think the editing of enum using OptionGroup items should be the default behaviour in this case. It’s so strange that the binder can’t guess automagically the enum values by calling a simple enum.values() and putting them into an OptionGroup.

What do you think?

2

Found the solution by myself 1 minute after posting (Murphy rules): Simple as adding the class I want to use as an editor.

mainLayout.addComponent(binder.buildAndBind("State","state",OptionGroup.class));

Lesson learned: If you think Vaadin doesn’t have what you need, you’re probably wrong, or doing it in the wrong way.
You guys did an awesome work!

3

Actually, it seems FieldGroup (well, actually, DefaultFieldGroupFieldFactory that it uses as its default field factory) knows how to bind enums quite well. There’s just a minor problem:
ticket #10975
. It’s debatable whether it’s a bug or a missing feature, but the workaround is easy:

mainLayout.addComponent(binder.buildAndBind("State", "state", OptionGroup.class));

It’s not clear at all that OptionGroup would be the best “default” field for enums, anyway.

4

Oh yeah we can agree on that. It’s the best in my actual case but not for all, sure.
What’s important is that a default field is provided if not specified, without throwing an exception.

Another workaround could be to write an hint on the exception message, as well.