On Tue, 16 Jul 2002, Leif Hanack wrote:
> with jstl i still can set a new value:
>
> <c:set target="${user}" property="name" value="newname"/>
>
> why?! is this a bug?!
>
> it seems as if the EL does not care about which interface i defined.
> he always work on the real object type.
>
> any help?!
Indeed, this is the specified behavior, and nothing else is really
possible in Java. When you say "the EL does not care about which
interface I defined," this is only partially true; it's actually the Java
language that doesn't care about the interface you defined. You've
created an object and then stored it in a collection of Objects; the type
of whatever reference you may have originally used is no longer relevant.
Whatever Object you added as a scoped variable is, in other words, an
Object in its own right, implementing certain interfaces, extending
certain superclasses, and instantiating a particular class. There is no
way to recover information about how you retrieved this object.
If you don't want to let the user set information on an object with
<c:set>, it must not have setter methods. You can always wrap the
underlying object in a wrapper that provides only one-way access, but an
interface does not provide this protection.
--
Shawn Bayern
"JSTL in Action" http://www.jstlbook.com
(coming in July 2002 from Manning Publications)
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