I was surprised to see, in Component.setDefaultModelObject(), the following code:
       // Check whether this will result in an actual change
       if (!getModelComparator().compare(this, object))

getModelComparator() being down to, by default, a simple equals between the present model object and the object to set.

This setDefaultModelObject is called from updateModel of FormComponent.

Why is that ?

AFAIK, it brings quite some disadvantages:
- adds quite some cost (equals test can be quite expensive, and are always more than just assigning a reference) - if equals isn't properly implemented, can be either meaningless (default equals being different instances are never equals even if logically equal) or not appropriate (in entities, my equals is based on the id, which when editing obviously causes an issue here) - IModel implementations don't behave like that (setObject for a PropertyModel or a Model don't check for non equality)

Yet I don't see any added value...

In the end, I see potential for misbehavior or unexpected one and no added value.

So, why it it this way ?

thanks in advance

Joseph Pachod

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