[Springframework-developer] Indexed and mapped properties

[<jue...@we...>]

I've just introduced preliminary support for indexed and mapped =
properties to BeanWrapperImpl, including test cases on the bean wrapper =
and form controller level. The current implementation is XP-style, i.e. =
"the simplest thing that might possibly work": It does not aim to offer =
a generic object graph navigation language like OGNL bur rather just the =
ability to traverse arrays, lists, and maps.

Consider a bean with the following properties, each containing 2 =
NestedBean instances:
- NestedBean[] myArray (of size 2)
- List myList (containing 2 NestedBean instances)
- Map myMap (containing 2 NestedBean values with String keys "key" and =
"key2)

NestedBean has a "name" property of type String that can then be set in =
the various instances as follows, for example as HTTP request =
parameters:
- myArray[0].name
- myArray[1].name
- myList[0].name
- myList[1].name
- myMap[key1].name
- myMap[key2].name

The map handling also supports the following alternative notations, so =
that JSP EL and OGNL syntax can be applied too:
- myMap['key1'].name
- myMap["key2"].name

Altogether, this should allow for populating a wide range of nested bean =
instances: simple nestings, arrays, lists, String-keyed maps. Note that =
it is *not* supported to *set* array/list/map elements yet: In a typical =
web app, new elements are created via special commands, not directly =
from a request parameter - but the bean properties of indexed elements =
need to populated directly from request parameters.

The beauty of it is that there are just a few lines of code in =
BeanWrapperImpl involved now, and that custom editors are nicely =
inherited. Of course we can try to add full-blown languages like OGNL =
later: I just don't see an easy way to combine this with our =
BeanWrapper's own capabilities.

Finally, a special feature for custom editor registration: You can not =
only register an editor for a property of a specific bean with an =
expression like "myArray[0].name" but also for a property of all beans =
in an array/list/map with "myArray.name". This is particularly =
convenient as it is the normal case: If a custom editor for an array =
element has to be registered, it should typically apply to all elements.

Juergen


DI J=FCrgen H=F6ller
Senior System Architect
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