Re: [Springframework-developer] non-String keys for map entries

[Darren D. <da...@da...>]

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On Tuesday 27 April 2004 10:21, j=FCrgen h=F6ller [werk3AT] wrote:
> A colleague of mine just suggested that <entry> tags in XML bean
> definitions should also support non-String keys: After all, a
> java.util.Map can take any Object as key.
>
> So instead of just the current:
>
> <map>
>   <entry key=3D"myKey">
>     <ref bean=3D"myTarget"/>
>   </entry>
> </map>
>
> We could also support something like the following:
>
> <map>
>   <entry>
>     <key>
>       <ref bean=3D"myKey"/>
>     </key>
>     <ref bean=3D"myTarget"/>
>   </entry>
> </map>
>
> The problem is the syntax: It looks odd to have the <ref> Map value at
> the same level as the <key> subtag, with the latter having a nested <ref>
> again...
>
> Any ideas?


<map>
  <!-- as now: String key -->
  <entry key=3D"myKey">
    <ref bean=3D"myTarget"/>
  </entry>
</map>


1.  consistent DTD
<map>
  <!-- kludgy..? symbolised bean reference -->
  <entry key=3D"@myBean">
    <ref bean=3D"myTarget"/>
  </entry>
</map>

2.  add ref to DTD attr list for map/entry
<map>
  <entry ref=3D"myBean">
    <ref bean=3D"myTarget"/>
  </entry>
</map>

Both suffer from losing the ability to declare 'local' or 'bean' but that=20
might not matter since neither may be capable of being validated via DTD=20
anyway - I'm no DTD expert.

Both are backward compatible though - if we go with <key> as an element=20
rather than an attribute, existing context definitions will break won't=20
they (unless the String version remains as an attribute which would be=20
somewhat confusing I think)

I wonder though what the use case would be.  I think using objects other=20
than strings as map keys is a common requirement in application code, but=20
in setting up a context?  I'm not sure - did your colleague have a=20
particular scenario in mind that could better be handled with such a=20
change, or was it a discussion item?  It'd be interesting to know!

=2D --=20

Darren Davison
Public Key: http://www.davison.uk.net/key.jsp
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