Mapping 2 form:input tags to handle dynamic Map<String, String> command field

Ok, I've got what seems to be kind of an unusual case. For a specific application we have created a kind of image metadata tracker that generates an xml file for us, the purpose of which is to tell our application what dimension symbols apply to a specific drawing. These are stored as String symbol and String dimensionName in a database table. (We have several hundred drawings, hence the need for this).

Toward that end I have the following command field which I need to be able to populate in a jsp:

Code:

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private Map<String, String> dimensions;

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with something along the lines of this:

HTML Code:

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<form:input path="dimensions.key"/>
<form:input path="dimensions.value"/>

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Now obviously that is invalid and doesn't work; My question is, how would I go about doing what I'm trying to do? I'm hoping to avoid javascript but whatever it takes to get this working.

Note: I'm currently using Spring 2.5.6, and need to get this working under that framework. However we're also planning a future upgrade to Spring 3 and I understand the method of handling this stuff will be different, so if you happen to be able to provide support for both the spring 2.5.x method and the 3.0.x method it would be greatly appreciated :)