[Springframework-developer] FieldError and nested properties

[Rob R. <rob...@ur...>]

Got a question about FieldError and validation. I know it's
created by DataBinder, and the ctor for FieldError creates three
codes for message lookup, which is nice. However, we'd like for
additional codes to be generated in the case of nested
properties.

Our problem is that we have several different UI's where
coordinate information is entered, but the coordinate properties
are at different nested paths, so we can't have something like
"typeMismatch.latitude.degrees". Instead, we'd need to do
"typeMismatch.someObject.someProperty.latitude.degrees" and so
on for all of the different objects that have coordinate
properties. 

We're going to write a NestedFieldError class that looks for
nested properties in the "field" value when a FieldError is
constructed. This will allow us to have a generic
"typeMismatch.latitude.degrees", or even a
"typeMismatch.degrees" error message, which will be very nice.
Unfortunately, this will involve extending DataBinder as well so
that it uses our NestedFieldError class. We'll have to override
the bind method.

I'm wondering - has anyone else needed this functionality? Would
it be too special-case to add it to the Spring validation
package? What could at least be done is to factor out how
DataBinder creates instances of FieldError - maybe toss it into
a protected method so that a subclass could easily override it,
or just refactor it into something pluggable and use the current
approach as the default.

Rob